A friend recently asked me about Leibniz’s position on death. Leibniz is very consistent on this question in his mature metaphysics (from the 1686 Discourse onward). Essentially, he denies death, affirming the immortality of the soul. In part, this is due to his commitment to the substantiality of minds or monads: monads must be individual substances, because there is unity in formed matter, but matter has no principle of unity in itself; and substances are by definition imperishable. (He even says at some point: it’s not so weird to insist that monads are indestructible, with no beginning or end; it’s no different, after all, from what the Gassendists say about their atoms.)
Each soul/mind/monad is characterized — this is literally its principium individuationis — by a proportion of clarity-distinctness and obscurity with regard to the expression or perception of the actual infinity of the world. In other words, you and I both perceive-express the same whole, but we express different parts of it with different degrees of clarity, and the rest only obscurely (and obscurity also admits of degrees). What we call death is when that ratio skews almost entirely in favor of the obscure, or, we might say, when the ratio of clear to obscure perceptions itself becomes infinitesimally small.
I like to imagine each soul as represented by a downward facing parabola; the height of the curve indicates the level of activity or freedom of the soul, since it clearly expresses everything beneath it. And freedom is essentially a function of the degree of understanding or intelligence, i.e., how much is clearly perceived. As we move right the y-value of the curve approaches -∞, or what is the same, the ratio of obscure perception (above the curve) to clear perception (beneath the curve) approaches ∞. And for the same reasons the level of understanding and freedom of the mind becomes infinitesimally small, as its confusion becomes infinite and it becomes infinitely passive. This process is indexed to the dissolution of the soul’s body, and we call it death. But the soul never finally goes out of existence, and it seems to follow that there is no kind of afterlife or otherworld.
That said, it’s not especially obvious how to square this conception with his Christological proclamations about the ‘great future’ of the City of God or the Kingdom of Heaven, which he says we know of not through reason but through revelation. Sometimes his language suggests that this world just is the Kingdom of Heaven, in which the moral order of grace, with its just punishments and rewards, is a fait accompli, whether we recognize it or not; at other times it’s hard not to think he has in mind a more classical notion of a Christian afterlife, even though he is quite explicit in arguing that the soul is inseparable from the body.
Here are some relevant passages.
“What becomes of the souls or forms at the death of the animal or at the destruction of the individual unit of organized substance? This question is the more difficult, insasmuch as it hardly seems reasonable that souls should remain, useless in a chaos of confused matter. This led me at length to conclude that there is only one reasonable view to take — that of the conservation not only of the soul but also of the animal itself and its organic machine, even though the destruction of its grosser parts may have reduced this machine to a size so small that it escapes our senses just as it did before birth. Moreover, no one can mark exactly the true time of death, which may for a long time be taken to be a simple suspension of observable actions and in the last analysis is never anything but this in the simple animals. Witness the resuscitation of flies which have been drowned and then buried under powdered chalk, and a number of similar examples which suffice to show that there would be other resuscitations, in cases much further gone, if men were in a position to restore the mechanism. … It is natural, then, that animals which have always been living and organized (as people of great penetration are beginning to recognize) will also always remain so. And since an animal has thus no first birth or enitrely new generation, it follows that there will be no final extinction or complete death, in a strict metaphysical sense, and that as a result, there is no transmigration of souls but only a transformation of the same animal, as its organs are differently folded and more or less developed.” (New System on the Communication of Substances §7)
Leibniz constantly reiterates that ‘the Cartesians’ (he also means to implicate the occasionalists) don’t distinguish between perception and apperception, and so don’t realize that there are perceptions of which one is unaware. This “led them into the popular confusion of a long stupor with death in a rigorous sense, which made them support the Scholastic prejudice that souls are entirely separate, and even confirmed some ill-balanced minds in a belief in the mortality of the soul.” (Monadology §14)
“When there is a large multitude of small perceptions with nothing to distinguish them, we are stupefied, as when we turn continuously in the same direction several times, so that a dizziness overcomes us and we grow faint and can distinguish nothing. Death can produce this state in animals for a time.” (M §21)
“The soul only changes its body little by little and by degrees, so that it is never deprived of all its organs at once; there is often metamorphosis in animals but never metempsychosis or the transmigration of souls. Neither are there entirely separated souls or higher spirits without bodies.” (M §72)
“It is because of this, too, that there is never complete generation, or, strictly speaking, perfect death, consisting in the separation of the soul. What we call generation is a development and an increase, just as what we call death is an envelopment and a diminution.” (M §73)
“These same Cartesians think that only spirits are monads and that there is no soul in beasts, still less other principles of life. And after having defied the everyday opinion of men too much in denying that beasts have feeling, they adjusted their views too far to popular prejudices, on the other hand, when they confused a long stupor coming from a great confusion of perceptions with death in the rigorous sense, in which all perception would cease. This has confirmed the poorly grounded opinion that certain souls are destroyed and has supported the pernicious view of certain so-called free-thinkers who have denied the immortality of our souls.” (Principles of Nature and Grace §4)
“Just as animals in general are not completely born in conception or generation, neither do they completely perish in what we call death, for it is reasonable that what has no natural beginning also has no end within the order of nature. Thus, abandoning their masks or their rags, they merely return, but to a finer stage, on which, however, they can be as sensitive and as well-ordered as on the larger one. And what has been said about grosser animals takes place also in the generation and death of spermatic animals themselves, that is, they are enlargements of other smaller spermatic animals, in proportion to which they can be considered large, for everything in nature proceeds to infinity. Not only souls, therefore, but animals as well, cannot be generated or perish; they are only developed, enveloped, reclothed, stripped, transformed. Souls never leave the whole of their bodies and do not pass from one body to another entirely new to them.” (PNG §6)