Keeping Them With You: Spinoza, Love, and Eternal Minds

2.1. Knowledge and commonalities

Spinoza differentiates three kinds of knowledge (cognitio): knowledge of the first kind is ‘opinion’, or more often ‘imagination’, knowledge of the second kind is ‘reason’, and knowledge of the third kind is ‘intuitive knowledge’ (E2p40s2). Adequate ideas are generally acquired through the second and third kinds of knowledge. By contrast, the first kind of knowledge refers to ideas we acquire through ‘fortuitous encounters with things’ (E2p29s). The first kind of knowledge arises when we, as finite things, encounter other finite things that differ from us and form ideas of them (E2p40s2). Knowledge of this kind is ‘the only cause of falsity’ and is the source of all inadequate ideas (E2p41, E2p41dem). The first kind of knowledge could include cases such as bumping into an object and forming an inadequate sensory idea of it, listening to some hearsay and gaining some inadequate idea of the thing discussed, attempting to learn how to build a house through trial and error and considering its varying levels of success, and so on.

Unlike the inadequate first kind of knowledge, ‘knowledge of the second and of the third kind is necessarily true’ (E2p41). The second kind of knowledge is based on ‘common notions’ and derivations from them. A ‘common notion’ denotes something that two things share fully in common. What we grasp through a common notion, or through what we share in common with another thing, cannot be grasped inadequately. Spinoza explains how this works in E2p39dem, and then explicitly names ‘common notions’ in E2p40s2. The proof for the perfection of knowledge based on common notions turns on God’s ideas of two bodies interacting, and on how God’s ideas relate to the human mind, but pursuing this proof would take us too far afield. For present purposes, note simply that when a person shares something in common with a body with which one is interacting, one can adequately understand whatever is common to themselves and that body. Anything derived from these commonalities using proper geometrical reasoning, further, cannot fail to be true (E2p40s2). For example, all bodies share in extension (it is common to them), and so we, as bodies, can adequately know things about the extension of other bodies. That is, we have a common notion of extension. We can thus also derive claims about the extended, geometrical properties of other bodies through our shared extension, thereby enabling us to know various scientific matters concerning natural bodies.

Spinoza further allows knowledge of commonalities beyond the basic features all extended bodies share (i.e., beyond extension, motion, and rest, which are named in E2p13L2dem). For example, he notes that the mind can adequately grasp more things about others the more one’s body shares things in common with other bodies (E2p39c), and that the mind is more able to ‘perceive’ things when the body is capable of being ‘disposed’ in many ways (E2p14). This makes natural sense: our bodies can take on new properties as they are affected, and so may come to share more in common with others.¹⁷ So, because I share things in common with other humans (e.g., we all need food to satisfy our essential striving), I can adequately know certain basic things about other humans (e.g., their striving-unto-food). Striving for food is something that is as much present in another human as it is in me: we strive to be as powerful as possible, and we both need sustenance to do so. It seems that Spinoza thinks we are both capable of, and have good reason to, form commonalities with others beyond the basic universal ones, and thereby also to make it possible to understand other things in ways that go beyond the basic universal commonalities they share with us.¹⁸

Further, if we can come to understand a thing’s essence as it follows from the essence of an attribute (as it follows from the nature of extension or of thought), then we have intuitive knowledge, or the third kind of knowledge (E2p40s2). Knowledge gained through intuition is known on the basis of a thing’s essence, and is also known as following necessarily from the order of nature, and so is understood without regard to duration. A square always has four sides, as that’s simply the nature of a square, and a human always strives for its power-maximising ends, as that’s just the nature of humans (and everything else) (E3p7). While we could grasp many of these truths through demonstrations, or the second kind of knowledge,¹⁹ these things follow from the self-evident nature of squares and striving beings (Spinoza takes essence-as-striving to be self-evident, E3p6–7). And, once we grasp something on the basis of reason, we can know it by intuition without needing the careful steps of geometrical reasoning.²⁰

So, the second and third kinds of knowledge are our two general sources of adequate ideas. However, while the first kind of knowledge is generally confused and produces all inadequate ideas, it can nevertheless serve as a stepping stone to at least the second kind of knowledge (and through it perhaps the third). Here is how that might work.

We can come into contact with a thing, develop an imagined idea of it, get dubious inadequate knowledge of it, and so recognise we should develop more properties to form more commonalities with it and thus know more. We can recognise when we are lacking an adequate idea of a thing by virtue of our being able to doubt our idea: adequate ideas have ‘all the properties… of a true idea’ (E2d4) and when we have a true idea we cannot doubt its truth (E2p43). So, if we find an idea of a thing dubitable, we know it cannot be true, and thus cannot be adequate. We can then know that we lack the commonalities necessary to develop indubitable adequate ideas, and thus aim to develop more in common with a thing. Through repeated exposure to a thing, we can move from a largely inadequate imaginative understanding of it on the basis of what we doubt about it, to knowing it better through more commonalities as we try out different things to be more like it. That is, we can develop commonalities and understand things by the second kind of knowledge, based on our new-found common notions, and based on derivations following from them.²¹ Once so grasped, we may even achieve intuitive knowledge of that thing. We can find by imaginative comparison what we doubt about a thing, and this identifies where we should try and develop commonalities that then enable adequate knowledge.

2.2. Knowing our loved ones

To see how we can apply this process of knowledge acquisition to knowing our loved one’s essences, we should first consider how Spinoza describes interpersonal love. Spinoza’s standard sense of love for a worldly thing, or, in our case, interpersonal love, is ‘joy, accompanied by the idea of an external cause’ (E3def aff6). We see some external thing as a cause of joy and thus love it. A further ‘property’ of love is ‘a will of the lover to join himself to the thing loved’, to maximise joy by achieving a ‘satisfaction in the lover on account of the presence of the thing loved’ (E3def aff6). That is, the lover wishes to form a union with the beloved to ensure the presence of the joy-causing object and thus maximise their joy.²² In light of Spinoza’s further comments on love in his early Short Treatise, it seems that the desired ‘union’ is of a very strong kind, where the union is the joining of the lover and beloved into ‘one and the same thing’. In the Short Treatise, Spinoza writes that ‘[l]ove is a union with an object that our intellect judges to be good and magnificent; and by that we understand a union such that the lover and the loved come to be one and the same thing, or to form a whole together’ (KV 2.5.6, emphasis my own).²³

Given this, I suggest that love compels us to produce commonalities with our loved ones. Suppose person P loves person Q. P thus takes Q to be a cause of P’s joy. Now, from here, love may make P either strive to make Q more like themselves, or make P strive to make themselves more like Q. In the former case, P may take Q to be a generally joy-causing being, and thus strive to make Q more like P in whatever ways that P thinks are good. This would ensure that P may continue benefitting from Q’s actions or presence, while making Q even more joy-conducive, and would seem plausible because P already thinks Q to be at least somewhat joy-conducive. For example, in doing our best to be loving rather than hateful, we will do our best to make others loving like us rather than hateful (E4p46dem), so that we may benefit further from them becoming loving individuals like us. One who is rational also, for example, strives to make others more rational, like themselves, through education, since the rational person knows that others will cause more joy (be ‘more useful’) the more rational they are (E4app9). So, if we love someone and already see them as joy-conducive, and see ourselves as rational or loving, we may want to make the person we love even more loving or rational like ourselves and thus even more joy-conducive, since we already know they are somewhat joy-conducive. Love can thus have us try to make others more like ourselves, insofar as (1) we see they are capable of causing joy in us, thus seeing them as joy-conducive generally, and (2) making them more like us further enables them to cause joy in us, which we think plausible because we already see them as somewhat joy-conducive.²⁴ In this case, if P loves Q, P will encourage Q to try out different properties until Q develops more commonalities with P, thus making P and Q more alike.

But the commonality producing nature of love can also work the other direction and make us want to be more like others. Again, suppose P loves Q and thus takes Q to be a cause of their joy. Because P understands Q to be joy-causing, P will want to be like Q for at least two reasons. First, P will want to be able to cause joy in others like they imagine Q does, since imparting joy on others is itself joyful (E3p30).²⁵ Second, P will want to become like Q so that P can cause joy in themselves even when Q is absent, given that ‘we strive to further the occurrence of whatever we imagine will lead to Joy’ (E3p28). P will want to ensure they enjoy whatever it is that lets Q cause joy even when Q isn’t present. P will thus strive to be like Q for both reasons. This direction of emulation should also feel somewhat natural to the Spinozist. For example, Della Rocca (2010: 179) holds that rational people want to become like those they see as rational,²⁶ and this fits naturally with my reading of love: when we encounter a rational person, they will be powerful,²⁷ and thus more likely to cause joy in us,²⁸ and so, naturally, we will love them and want to be like them in what makes them joy-conducive.²⁹

Love can thus push us to develop commonalities with the beloved, either by encouraging them to become like us, or by making us try to be like them (or both).^30,31 Perhaps the former represents how a parent teaches a child to navigate the world as a parent does, and the latter how a child strives to learn from a parent, but this should generalise to all interpersonal love. For brevity, I will mostly treat love restricted to the case where the lover tries to be like the beloved, but in principle it can flow in both directions.

Now, let us return to P and Q, where P loves Q and wants to become like Q. Let us consider how this leads to P being able to know Q’s essence. P can have some minimal adequate knowledge of Q when they come in contact through their common extension, motion, and rest. But P will also be repeatedly exposed to Q, and so various images of Q will become present in P’s mind. These images will, of course, constitute the inadequate first kind of knowledge insofar as P has differences from Q. But as we saw in §2.1, we can move from the first kind of knowledge to the second. P realises that much of their idea of Q is dubitable and therefore false and inadequate. P can then try developing more diverse properties. Once P lands on a new property which is actually common to Q, P can come to adequately learn more things about Q and also becomes more like Q.

As P tries to become more like Q in light of P’s love for Q, P will strive to copy whatever P adequately understands of Q more regularly. This forms the kind of ‘union’ Spinoza identifies, in which lovers become ‘one and the same’ (KV 2.5.6). P and Q will share more in common, and thus will be able to know each other even more by the second and eventually the third kinds of knowledge.³² And the more they become alike, the more the same things will be good for each of their strivings. They will therefore be better able to help each other and thus also see themselves as more power-enhancing and joy-conducive (E4p18s, E4p31c, E4p35c1, E4p34s). This, in turn, will further increase their mutual love, since they can more readily see each other as external causes of joy, and further reinforce their growth of commonalities as they are more encouraged to become like each other. The cycle of love and becoming alike is thereby self-reinforcing.

Now, as our strivings become more alike (like P and Q), we are more able to understand each other’s strivings. Many of the commonalities we develop will naturally be either commonalities in our bodily powers or will be commonalities in things that our minds understand,³³ and so will be commonalities we have with parts of a loved one’s essential striving.³⁴ For instance, P may find the way that Q plays music especially joy-conducive, and thus try to gain the same musical skills and knowledge as those that characterise Q’s essential power. If P can learn how to use their body to cause a particular effect on an instrument in the same way Q does, P can thus understand something that characterises Q’s power, both in terms of the physical skill itself and the knowledge or idea of it. Since knowledge of a thing is possible insofar as we enjoy commonalities with it, in developing commonalities in our bodily skills and mental knowledge, we become capable of adequately knowing parts of our loved one’s bodily skills or mental knowledge. To the extent that we can form an adequate idea of our loved one’s essence in our minds, we can thus keep the very same entity in our mind that remains of a loved one eternally.³⁵

2.3. Keeping a loved one with you

I will now explain some vital features of Spinozist ‘keeping them with you’. First, I’ve just said that to the extent that one can form an adequate idea of our loved one’s essence in our minds, one can ‘keep them with you’. Earlier, I also said that one could keep a loved one’s eternal something with them to a degree. These ‘to the extent that’ or ‘to a significant degree’ qualifiers therefore require clarification. Second, I will provide a more concrete example of a relationship in which ‘keeping them with you’ is possible, for further clarification. Finally, I will briefly explain why I take this ‘keeping them with you’ to amount to keeping one and the same numerical entity in one’s mind as remains of a loved one eternally, to whatever degree they grasp our loved one’s essence.

Now, given the self-interested biases and differing experiences of any two people’s respective essential strivings, two people may not share all relevant properties in their essences, even when they are pushed by love to become more alike.³⁶ As a result, they may never know each other’s essences entirely, given that they won’t have everything in common. Consider our friends P and Q. P’s idea of Q’s essential striving, or P’s idea of Q’s essence, may not adequately capture absolutely everything about Q’s essential striving. But as Hübner (2022a) has argued, adequacy of ideas (and other ‘epistemic phenomena’) can come in degrees, and adequate ideas can be parts of larger, not entirely adequate ideas. Insofar as we know parts of a given thing through the second or third kinds of knowledge, we know it adequately, and insofar as we fail to grasp other parts or imagine false parts of a given thing, we know it inadequately (or fail to know it). These ‘insofar’ qualifiers therefore yield, I suppose, degrees of adequacy. As such, one can have a varying degree of adequate understanding of their loved one’s mental and bodily power, and insofar as there is a degree of adequate knowledge, they can keep the loved one with them to that degree. Whatever degree is required to ‘keep them with us’ meaningfully may be difficult (or impossible) to pin down, but we can indeed ‘keep them with us’ to whatever degree we have adequate ideas of parts of their essential striving. As love continues to produce more commonalities between us and our loved ones, we will develop more commonalities in our strivings, thereby being able to understand more parts of our loved one’s essence, and thereby increasing the degree of adequacy of our idea of a loved one’s essence. Through our tendency to become like people we love, or make them more like us, we increase how much of a loved one’s essence we can adequately know.³⁷

Let me give a more practical example than those provided by P and Q. Suppose you are the child of a devoted and loving parent. You see your parent as the cause of your joy: when they are around, you typically feel joyful (they help you with your homework, feed you, play with you, etc…). You thus come to love them. You do your best, then, to become like your parent, to develop what you take to be joy-conducive properties and thus get to experience joy more often and cause it in others. You can know something limited about your parent in light of what you share in common with them as extended things, for example that they move, they rest, etc. Of course, these things are only minimally joy-conducive. You want to develop further commonalities, to be more like a joy-causing thing, and so you wish to know more about them beyond these basic commonalities. As a result, you try to take on more properties. You observe your parent enjoying cooking, and you don’t understand the art or have an adequate idea of the intricacies you observe while they cook. You do your best to come to know their cooking: you repeatedly spend time with them, discuss cooking with them, and through trial and error, learn their cooking skills. That is, you learn how to exercise your body to cause effects in the food or cooking tools in the same way as your parent. The two of you develop a new commonality in your bodily capacities (the cooking skill) and your mental understanding (the knowledge of the cooking skill). You could thus adequately know a part of their essence, namely, the part constituted by their cooking skills and knowledge of it.

And recall, the commonality-producing tendency of love can work both ways. Your parent may love you, for example, and want you to become more like them. They encourage and engage in your efforts to learn their cooking skills, and point out when you develop commonalities in skills as you come to more closely match their cooking. This speeds up the process, and explains the commonality-producing tendency of love in the other direction.

As a result of both directions of love’s commonality-producing property, you can eventually adequately know the idea of cooking that your parent has in their mind. You thus, in bringing that idea of cooking into your mind, have the very same idea in your mind that characterises a part of their mind’s power or essence. And since your parent’s cooking, as an activity, is part of their bodily power of acting, you thereby also know something about their body’s power of activity: you bear in your mind now, to whatever degree you understand your parent’s cooking, the idea of the very same bodily power that comprises part of their essence, and thus the idea that comprises part of their eternal something. This process can be mirrored by a variety of other forms of knowledge and capacities. Some developed commonalities, like learning and then speaking a common language, could further accelerate the development of other commonalities insofar as they facilitate the future learning process. And insofar as you do this with more and more capacities or knowledge that are part of your parent’s essence, you can retain an even greater portion of their eternal something in your own mind: more and more of the very thing that is eternal of your parent is present in your own mind. Once you have the idea of parts of your parent’s essence, you can keep those parts with you beyond their death. To whatever extent you adequately know your parent’s essence, the same idea that constitutes the eternal something of your parent remains in your own mind.

Lastly, I should say why I believe that this amounts to keeping numerically the same entity in your mind as is the eternal something of a loved one, at least to a degree. That is, I must clarify why this amounts to having in your mind parts of the very same idea that comprises their eternal something, rather than simply having a different token of the type of idea.

Now, I have already established that to ‘keep them with you’, you must have adequate ideas of parts of your loved one’s essence, and to the degree you adequately understand parts of that essence, you can ‘keep them with you’. Note that adequate ideas are always true ideas (E2p34, Ep60) and that ‘a true idea must agree with its object’ (E1a6).³⁸ However, two numerically distinct true ideas, I₁ and I₂, would have to differ in some way.³⁹ As such, they could not both agree with their object—they could not both be true. If I₁ agrees with its object, whatever I₂ has or lacks that differentiates it from I₁ will also mean it does not agree entirely with its object. But this is absurd, since they are both supposed to be true ideas. As such, I₁ and I₂ must be numerically identical ideas. Since this holds for true ideas, it must hold for our adequate ideas, given that true ideas are also adequate ones. Thus, it holds that the adequate idea of part of a loved one’s essence which remains eternally in God’s mind is numerically identical to our own adequate idea of that part of a loved one’s essence. Whatever parts of our idea of a loved one’s essence are adequate, then, are going to be numerically identical with those parts of God’s eternal idea of a loved one’s essence. Indeed, Spinoza makes use of the tenet that, when we have an adequate idea of something, it is the very same numerical idea of that thing that God has: in various parts of E2p39dem–E2p43s, it is implied that if we have an adequate or true idea of a thing, it is numerically the same as God’s idea of the thing. For example, Spinoza writes that ‘our Mind, insofar as it perceives things truly, is part of the infinite intellect of God (by E2p11c); hence, it is as necessary that the mind’s clear and distinct ideas are true as that God’s ideas are’ (E2p49s), with the inference obviously depending on our true ideas being the very same ones as God’s true ideas (this is what ensures our clear and distinct ideas are as true as those of God). So, if we have an adequate idea of part of a loved one’s essence, that idea is going to be numerically identical with God’s idea of that part of their essence. Thus, our idea of that part of their essence is numerically identical with the idea that remains eternally of that part of their essence in God’s mind.

Going back to the earlier example, if I understand my parent’s cooking skill adequately, have the same cooking ability as them and have the same cooking knowledge as them, then I can adequately have the very same numerical idea of the part of their essence that is composed of their cooking powers/knowledge as is part of God’s idea of their essence. Part of their eternal something is literally kept with me in my mind. Again, we can keep progressively more of their eternal something ‘with us’ the more we develop commonalities. Moreover, I am not alone in holding that two minds can have the very same numerical idea (as in when we share the same idea of cooking as our parent). Nadler, for example, thinks that two minds could acquire the very same adequate ideas during life, not even differentiated with respect to the perspectives of each mind: ‘What is to keep two minds from having acquired in this life exactly the same collection of adequate ideas? Since adequate ideas reflect reality sub specie aeternitatis, there would not even be any difference of perspective on the objects so cognized’ (2002: 125).⁴⁰ All adequate ideas consider their object from God’s eternal perspective, and thus are the same, undifferentiated even by perspective.^41,42

The numerical identity of parts of the idea of an essence in our mind and in God’s is hard to conceptualise, but we can think of this roughly like so: suppose the adequate idea of a loved one’s essence is comprised of content {x, y, z}. So, x, y, and z are ideas of a loved one’s bodily capacities or mental understanding. God’s adequate idea of the loved one’s essence will just be {x, y, z}. To the extent that we have an adequate idea of our loved one’s essence, our mind might grasp a portion of God’s idea. To illustrate this, suppose our mind’s ideas of things not related to our loved one are [a, b, c] (in square brackets). Suppose we grasp x and y of our loved one’s essence, but fail to capture z. The mental situation would then look like [a, b, c, {x, y,] z}, with the square brackets denoting our own mind and the curly brackets denoting God’s idea of our loved one’s essence. We can see how our mind encompasses portions x and y of God’s adequate idea of a loved one’s essence. Our mind thus comprises, in this instance, some numerically identical parts of God’s idea of a loved one’s essence. It is just that our mind is able to incorporate a significant portion of the very same numerical idea that remains eternally of our loved one, and to that extent keep the very same entity that is eternal of them in us. Our mind enjoys a partial identity with the exact numerical entity that remains of a loved one, insofar as parts of our mind are composed of the very same numerical parts as those composing the eternal something of a loved one. Insofar as we do not succeed in developing all the same capacities or knowledge (and do not have identical causal histories), the identity will not be absolute; we will not keep our loved one’s eternal something with us entirely. But insofar as we do develop the same bodily capacities and the same adequate ideas, we may, in our own mind, keep with us some meaningful part of the exact same numerical entity that remains of a loved one.⁴³

2.4. The Balling letter

With these preliminaries in place, we can at last turn to Spinoza’s July 1664 letter to Pieter Balling.

After the death of Balling’s son, Balling wrote to Spinoza describing how he had anticipated his son’s death through ‘omens’, to which Spinoza responded with what we might regard as a naturalistic explanation of Balling’s experience.⁴⁴ I set aside this aspect of the letter, what matters for present purposes is that Spinoza makes a claim that is directly relevant to my account of ‘keeping them with you’. For Spinoza, Balling so loved his son that they became ‘as it were, one and the same’, just as love has us do in the Short Treatise. I will argue in this section that this claim about Balling and his son constitutes an example of two people developing commonalities in their essential striving through interpersonal love. As I have argued, Spinoza’s epistemology entails that we can know a loved one’s essence to the extent that our striving or power has things in common with theirs, and that this enables our ‘keeping them with us’. As such, if my reading is correct, and Balling and his son come to enjoy common features in their essences, then Balling could have kept his son with him in the way I have outlined (whether or not he in fact did so). If we see here an example of someone coming to enjoy essential commonalities with a loved one as a result of their love, then we can identify an actual instance in Spinoza’s corpus in which my account of Spinozist ‘keeping them with you’ is possible. Let us consider the relevant extract of Spinoza’s letter at length:

To take an example like yours, a father so loves his son that he and his beloved son are, as it were, one and the same (quasi unus, idemque sint). According to what I have demonstrated on another occasion, there must be in thought an idea of the son’s essence, its affections, and its consequences. Because of this, and because the father, by the union he has with his son, is a part of the said son, the father’s soul must necessarily participate in the son’s ideal essence, its affections, and consequences. (Ep17)

In this passage, Spinoza suggests that Balling and his son, joined by love, can become ‘one and the same’, that Balling can be ‘part’ of his son, and can ‘participate’ in his son’s ideal essence. I suggest that Spinoza thinks this is possible because, by striving in light of their love to become more alike, they can come to share significant commonalities in their essences.⁴⁵ Love, of course, must be what produces the relevant features of Balling’s relationship with his son, since it is what Spinoza cites explicitly as making the father and son ‘one and the same’. And Balling, it seems, can ‘participate’ in the idea of his son’s essence that persists in the attribute of thought (the ‘ideal essence’ that ‘must be in thought’), suggesting that he can literally ‘participate’ in his son’s eternal something. This aligns quite nicely with the account I’ve given of how love can produce essential commonalities and make it possible to know a loved one’s essence, and thus to keep in one’s mind the very thing that is eternal of them.

As evidence for this reading of the letter, we should look to where Spinoza deploys the concept of two individuals enjoying commonalities in nature or essence. If these passages reveal that people sometimes enjoy commonalities in their nature or essence, we can read how Balling and his son came to be ‘one and the same’ and could ‘participate’ in each other’s essences.

At E4p18s, Spinoza deploys the idea of multiple people enjoying the same nature and becoming ‘joined’ to one another, and that this is what happens when they ‘agree in all things’:

For if, for example, two individuals of entirely the same nature are joined to one another, they compose an individual twice as powerful as each one… Man, I say, can wish for nothing more helpful to the preservation of his being than that all should so agree (convenient) in all things that the Minds and Bodies of all would compose, as it were (quasi), one Mind and one Body. (E4p18s, emphasis my own)

In this passage, the way that people can come to ‘agree in all things’ and thus enjoy the same nature is what will help us.

Spinozist ‘agreement’, generally, is about having commonalities, and this can be supported by what is further found in E1p17s.⁴⁶ There, Spinoza claims that people can ‘agree’ and thus come to enjoy the same essence: Spinoza says explicitly that while two humans cannot enjoy the same numerical existence in their lives and must remain in different bodies (‘in existence they must differ (differe)’), they can have essences which ‘agree entirely’ (prorsùs convenire) (E1p17s). When people’s essences ‘agree entirely’, they have commonalities in essence, or, given that our essence is our power, the same powers. That is, two people can enjoy commonalities in essential power in different existences.⁴⁷ In such cases, ‘if the essence of one could be destroyed, and become false, the other’s essence would also be destroyed’ (E1p17s).⁴⁸ The agreement they enjoy must thus be in having the same things characterise their essential striving or power. This makes it so that, if one’s essential powers are destroyed, so also are those that characterise another person’s essence. While yet ‘if the existence of one perishes, the other’s existence will not thereby perish’ (E1p17s), their essences are characterised by the same kind of powers. This informs how agreement leads people to enjoy commonalities or agreements in ‘nature’, as they do in E4p18s.

We can thus see how Balling and his son come to be ‘as it were, one and the same’: people can have ‘agreements’ in their natures, and to that extent their essences are characterised by the same kinds of powers (both bodily and mental). When they have (largely) the same powers, the properties that characterise their essences (how they strive) must ‘agree’ or be the same, and so they to that extent become ‘one and the same’. Indeed, this should make intuitive sense given my discussion of love as producing commonalities, and also Spinoza’s claim that it is through love that Balling and his son became ‘one and the same’.

Finally, and emphatically, the Latin deployed in the Balling letter is also especially revealing. The Latin that describes Balling and his son as one and the same is as follows: ‘pater (ut tui simile adducam exemplum) adeò filium suum amat, ut is, & dilectus filius quasi unus, idemque sint’ (Ep17). This mirrors the Latin that Spinoza uses when establishing the numerical identity of a mode of extension and its corresponding mode of thought: ‘Sic etiam modus extensionis, & idea illius modi una, eademq́ue est res, sed duobus modis expressa’ (E2p7s). It also mirrors the Latin used when Spinoza identifies will and intellect as numerically the same thing: ‘Voluntas, & intellectus unum, & idem sunt’ (E2p49c). In each extract, we see, respectively, the use of unus, una, and unum (all modifications of unus), and of idemque, eademque, and idem (all modifications of the same root word idem, with an additive que in two cases). In each case, the ‘being one and the same’ is explained with the very same language (save for the quasi in the letter, to be discussed shortly). And, lastly, other commentators have treated the way that lover and beloved become ‘one and the same’ in the passage on love in the Short Treatise as being about numerical identity.⁴⁹ It is widely accepted that, for Spinoza, a body and its mind are the same mode of substance, and also that will and intellect are numerically the same thing. So, if the same language is used in the Balling letter to describe Balling and his son becoming one and the same, and the loving union of the Short Treatise is about numerical identity, then we should take seriously the view that the ideas of Balling’s essence and of his son’s essence are at least partly numerically identical, insofar as they are characterised by ideas of the same powers. That is, the two of them enjoy commonalities in their essence, and thus can know parts of each other’s essences adequately, and so keep each other ‘with them’ after the other’s death.

The letter’s language concerning Balling and his son being ‘one and the same’ though, comes with a qualification. Spinoza, of course, thinks that Balling and his son cannot become entirely identical. They become only ‘as it were’ (quasi) one and the same. But, given my earlier discussion of knowing a loved one as a matter of degree, and there being degrees of ‘keeping them with you’, this qualification is actually quite natural. Insofar as people have parts of their striving or power in common, they become ‘one and the same’. That said, this is always a matter of degree. So, Spinoza must qualify his claim with a quasi. What differences Balling and his son retain make them not entirely identical, but having common powers makes the idea of their essential striving or power the same to a degree.

If this reading is correct, then we have textual evidence that ‘as a result of their love’, people can come to have commonalities in parts of their essences. As I’ve already argued, this makes knowing a loved one’s essence possible, and makes ‘keeping them with you’ possible to the degree that one knows parts of a loved one’s essence. Though Spinoza does not make these connections anywhere, the relationship he attributes to Balling and his son, his epistemology of commonality, his views on love, and his views of the eternal mind, demand that a Spinozist accept ‘keeping them with you’ as a real possibility for real people.

3.1. Love is not always sad, and can be power-enhancing

Recall that sadness is a passage to a lesser perfection (E3def aff3), so we should aim to avoid anything that produces it in us. This may reduce the significance of a Spinozist theory of ‘keeping them with you’: one might ask ‘so what if we can keep them with us? Such keeping is conducive to sadness, and thus Spinozistically useless or inert’. To object as such, an objector can point to Spinoza’s comment in E5p20s on the dangers of love: ‘sickness of the mind and misfortunes take their origin especially from too much Love toward a thing which is liable to many variations and which we can never fully possess. For no one is disturbed or anxious concerning anything unless he loves it’ (E5p20s). Since we can be disturbed by harms to, or the absence of, the things we love, interpersonal love can be the source of great sadness. And some of Spinoza’s discussions of undesirable passions even give specific examples of how love can lead to sadness. Longing, for example, is ‘a Desire, or Appetite, to possess something which is encouraged by the memory of that thing, and at the same time restrained by the memory of other things which exclude the existence of the thing wanted’ (E3def aff32). We long for something when ‘we remember a thing that affects us with some kind of Joy’ (E3def aff32) but which we know can no longer be present, given conditions that exclude that thing’s existence. We might long for a loved one, then, by remembering them, and at the same time know that they’ve passed, and so their existence, in some sense, is excluded by the current state of things. Interpersonal love, when it leads to a longing to keep passed loved ones with you, may thus seem to provoke sadness.

But this objection is solvable. If love permits us to grasp something eternal of a loved one, in the way I’ve suggested, then we do not need to suffer a longing for the loved one. Someone who longs for a loved one is holding in their mind something which is really gone. They are picturing the loved one as a person with a memory and imagination as much as a person characterised by an essence or power, and so are picturing something that truly passes when the loved one perishes (see E5p21). But if we call to mind only the parts of the eternal something of a loved one to which we have access, then we cannot be subject to longing. There is nothing which can ‘exclude the existence’ of a loved one’s eternal something because the eternal something is eternal, it ‘remains’ (remanet, E5p23) no matter what, and so can always be brought to the mind to whatever degree someone comes to know it. When considering only a loved one’s eternal something, we only consider something that is truly existent, and so run no risk of a sad longing, or indeed any other sad passion that comes from loving a thing ‘which is liable to many variations and which we can never fully possess’ (E5p20s). To whatever extent one understands it, a passed loved one’s eternal something is, of course, neither liable to variation nor unpossessable.

This is also why Spinozist ‘keeping them with you’ is different from mere memory of a passed loved one. For Spinoza, remembering is just what happens when we encounter something and then bring to mind, through what we are accustomed to seeing alongside that something, another thing that is not necessarily present (E2p17s): for example, we hear ‘apple’ and immediately recall an image of an apple. Yet, if we call to mind a loved one’s eternal something, we hold in our mind the exact thing which ‘remains’ of someone’s mind after their death to whatever degree we adequately know it, and so it is necessarily present to us. It will not be a mere conjuring of something which may be absent, but a coming to enjoy something that necessarily is.⁵⁰

Further, we can identify Spinozist motivations to keep our loved ones with us, showing the desirability of the love required to achieve it and the therapeutic value of ‘keeping them with you’. Whether Spinoza himself would identify the benefits I outline here is unclear, but these benefits are certainly implied by his views. There are at least two ways that keeping our loved ones with us enhances our power or joy. These ways will provide further evidence against the objector’s view that ‘keeping them with you’ can lead to sadness.

The first benefit of keeping our loved ones with us is that it demands knowledge of something as eternal, and so is necessarily power-enhancing. For Spinoza, ‘[t]o conceive things under a species of eternity… is to conceive things insofar as they are conceived through God’s essence’ (E5p30dem). The mind, when considering its own essence, knows itself as part of and following from God (E5p30). The same should apply to a loved one’s essence, as it would to anything else’s. So, when entertaining the eternal idea of the loved one’s essence, we are coming to know God (conceiving it ‘through God’s essence’), and for Spinoza, ‘[t]he greatest virtue of the Mind is to know God’ (E5p27dem). Indeed, knowing essences constitutes the intellectual love of God (E5p32c) which is an active enhancement of our nature and in fact its very blessedness (E5p36–E5p36s). Therefore, it is to our benefit to know and consider the eternal something of our loved ones.⁵¹

Second, in calling to mind the loved one’s eternal something, we will be bringing to mind an object of love. Recall that love, for Spinoza, is ‘joy, accompanied by the idea of an external cause’ (E3def aff6). Joy, you will also recall, is a passage to a greater perfection (E3def aff2). Insofar as we keep something of a loved one with us and call that something to mind, something of our loved one, who is associated with joy, will be present to the mind. And if a lover experiences the ‘presence of the thing loved’, then ‘the lover’s Joy is strengthened or at least encouraged’ (E3def aff6). As long as the thing loved will not later cause us more evil or sadness, we are strengthened by its presence. Clearly, an unchanging post-death essence will not later cause more evil or harm to us: it is unchanging! As such, it is good to bring it to mind and be strengthened by it.

3.2. Different readings of essences and eternality

One might also ask whether I need to commit myself to a certain reading of what it means for an essence to be eternal, even given my treatment of Nadler’s distinction between the ways the mind is eternal in §1. Objectors might suggest, for example, that I need to adopt something like Garrett’s view, according to which what is eternal of an essence, and so what persists as the eternal idea of a loved one, is only the formal essence of that loved one (most recently given in Garrett 2018, ch. 9). On Garrett’s view, a thing’s eternal formal essence is different from a thing’s essence when that thing is actually considered as existent. I.e., a formal essence differs from an actual essence. On the Garrettian view, what persists as formal essence in the attribute of thought is merely the idea of the formal content which would need to be actualised for a passed person to actually exist. What persists as formal essence in the attribute of extension is a pervasive feature of extension (an infinite mode of extension) that makes possible the actualisation of the body when it actually exists. Now if what persists is a Garrettian formal essence only, then there is no problem for me: someone can, through the ways I describe, come to know the conceptual content required for someone else to be actualised as a striving being, or what is required in extension for their body to be actualised— insofar as they develop commonalities with a loved one and make those features knowable.⁵² This might reduce the ‘wow-factor’ of the Spinozist theory of ‘keeping them with you’, but strictly speaking, it will not reduce the Spinozist possibility or value of ‘keeping them with you’.⁵³

The Spinoza interpreter may ask if I am committed to this because the main alternative, it seems, would involve following those readers who maintain that what persists is just the actual mind, though considered as necessary or essential rather than as contingent and durational. On this approach, the actual mind is either, for some examples, the mind considered (a) as having an eternal aspect (Grey 2014), (b) as under a certain aspect (Lærke 2016), or (c) from a certain perspective (Vermeiren 2023). In fact, though, I take it that my view is also compatible with this approach.

Suppose that what persists is the mind itself but considered differently than when alive, we will then run into prima facie issues. For example, some authors posit that the mind can cease to exist in duration while being ‘eternal’, since eternality is not strictly concerned with indefinite duration (that would be a thing’s mere sempiternity). When these authors consider what it means for the mind itself to be eternal, they regard its durational existence as irrelevant. All it means for the mind to be ‘eternal’ for (at least some of) them is that its existence follows necessarily from God’s nature (as does everything else’s; see E1p16–18). Recognising the mind’s eternality, or eternal something, for some of these interpreters, just means understanding a thing’s essence as it follows from God’s nature, rather than supposing there is something that extends through all durational time. As such, for some of these interpreters, the eternal something of the mind can in principle cease to exist in duration if it is not thought, whether or not it in fact does. Lærke, for example, writes that ‘eternity can last as long as you want, for a moment or for a long time’ and ‘it is simply irrelevant to its constitution which is rigorously a-temporal’ (2016: 278).⁵⁴ All that pertains to a thing’s being eternal, for these readings, is its being necessary. As such, would it not be possible for a loved one’s eternal something to cease being during the durational time in which I exist after them? On the contrary, this view, in addition to Garrett’s, is compatible with what I say. If we become through love sufficiently like our loved one, then when they pass, an eternal idea of their body’s and mind’s powers, and how they followed from nature, can still be present in our own mind. We can force the eternal something of a loved one to our own mind, and make its ‘eternity last as long as’ we are able to think it. This, again, will preserve the benefits I attribute to ‘keeping them with you’ in §3.2. The idea in our mind will be an eternal one, will exist in its durational reality (as long as this idea is thought), and will still be a source of joy.

3.3. Loving many with many differences

Lastly, one might ask if my reading implies that we can only love one person in the fashion requisite for ‘keeping them with you’, since we must develop commonalities with people, and different people will differ quite a lot. My reply is ‘no’. Again, we experience interpersonal love when we think that someone is the external cause of joy in us. We want to form commonalities with our loved ones so we can enjoy their joy-causing properties—or make them like us so they can enhance our own joy in the future. So, if I love my sibling and I love my significant other, I will find that each of them produces some kind of joy in me. What I want subsequently is to enjoy whatever it is in either of them that produces joy in me—or make them more like me insofar as I am rational or powerful. So, insofar as I take my sibling to cause me joy, I will want to be like my sibling in their joy-conducive capacity, and insofar as being like me could improve their capacity to impart joy, I might want to make them like me. The same is true of my significant other. If different parts of each of these people cause joy in me, respectively, I will want to be like them to the extent that they have different things that cause joy in me, and if different parts of me could make them more able to cause further joy in me, then I will strive to make them like me in different ways. That is, if I love my sibling because they have properties {x, y, z} that cause joy in me, and my significant other because they have properties {a, b, c} that cause joy in me, I will strive to be like my sibling in developing {x, y, z} in common with them, and also strive to be like my significant other by developing {a, b, c} in common with them. A similar pattern holds if trying to make them more like me: different properties of myself might be relevant in making them more powerful. Accordingly, I can form commonalities with two different people in light of different joy-conducive aspects of them or of myself.

But what about cases in which we love one person with properties {~a, b, c} because we associate those properties with joy, and another person with properties {a, y, z}? In this case, the two beloveds each have some property that contradicts a property of the other (~a and a, respectively), and I cannot become entirely like both. But all that this implies is that the degree to which we can all have essential commonalities is reduced, and I must determine whether ~a or a is more joy-conducive in establishing which commonality to build. This is fine for my view, I think, and indeed seems inevitable if we are going to consider how ‘keeping them with you’ could work in practice: some joyful parts of a loving relationship with people whose relationships with us differ cannot be made common to each person we love. Insofar as it is possible, though, we may enjoy different loving relationships with different people, form commonalities to different extents, make them further enjoy commonalities with us and with each other, and thus finally understand different parts of their essences to different extents. As such, depending on relevant circumstances, we may come to know just one, or very many, different people we love to whatever degree is required to meaningfully keep them with us.⁵⁵