Andrew M. Cavallo

Before asking "What is a person?", I would like to ask a more basic question, namely: In what sense is one individual, not necessarily human, distinct from another? What allows me to speak of this system as opposed to that system?

This problem of what it means to be an individual is closely related to my 2012 paper on the topological problem of system boundary, wherein I describe how a system often shares a boundary with its environment that permits the local entanglement of elements of the system with elements of the environment without thereby collapsing the environment and the system into one unit.

But a mathematical description of a system's boundary, no matter how precise, is not enough to resolve the identity dilemma. I believe, following Leibniz, that only a true unity can unite. An individual, or organized system of components, is therefore a true unit only if it has a governing monad: a true unity underlying the multiplicity of its components. In other words, whatever is, is one: true unity = being.

For Leibniz, there are three broad types of monads, namely:

1. Bare monads, which have perception.
2. Souls, which have perception, consciousness, and memory.
3. Spirits, or rational souls, which additionally possess apperception—the ability to grasp truth through abstraction.

Spirits are distinguished from souls by these higher capacities. Hence only spirits are capable of mathematics, metaphysics, and knowledge of God. Moreover, only spirits are capable of self-reflection, since the “I” is itself an abstraction representing an underlying truth.

Leibniz's argument for monads is considerably more interesting than the usual "building blocks" approach of the atomist. From a corporeal perspective, matter is not only infinitely divisible but in fact infinitely divided. Leibniz is thus not an atomist: there is no ground-level material object whose indivisibility can supply the true unity of an individual.

Monads, by contrast, are indivisible precisely because they are immaterial. Having no parts, they have neither form nor figure nor extension. Hence Leibniz describes monads as "simple." They are spatially simple but qualitatively complex: each monad is a qualitative multiplicity within a spatial unity. Far from existing in spacetime, Leibniz proposes a relativistic theory of spacetime as a property of monadic perception. Hence monads are antecedent to spacetime.

The identity of an individual therefore rests not in the persistence of its corporeal parts, but in its underlying monadic unity.

This distinction between being and function is already implicit in Leibniz's Monadology. According to Leibniz's principle of continuity, nature makes no genuine jumps. Discontinuities may appear to one, but deeper analysis reveals intermediate degrees connecting apparently discontinuous states. Leibniz applies this principle to perception: between clear consciousness and apparent unconsciousness lie innumerable degrees of increasingly minute perception.

Indeed, even while one is conscious, innumerable perceptions escape consciousness. A person writing a letter, for example, need not be conscious of the countless minute motions of the hand involved in forming each word. Much the same is true of a violinist performing a familiar passage. Hence perception need not itself be conscious.

The same principle applies in more extreme cases. In states such as dreamless sleep, fainting, and even death, a soul may cease to manifest the capacities characteristic of a soul and may resemble a bare monad, yet it does not thereby cease to be a soul; its higher capacities remain latent. Thus, the present manifestation of a capacity cannot determine the underlying nature of the individual.

The infinite division of matter also has an important consequence for organic life. Leibniz proposes a sort of pan-organicism, according to which every portion of matter, no matter how far one descends down the infinite ladder of divisibility, is alive. Nothing is dead; nothing is inert. Every portion of matter contains a world of living creatures, while every monad is a living mirror of the entire universe from its own point of view. Beneath every apparent organic part, therefore, lies further living organization without end. The organism is not a machine composed ultimately of dead matter, but an inexhaustible multiplicity of life whose true unity is supplied by its governing monad.

Consequently, radical corporeal change need not entail the destruction of the living individual. Leibniz describes what one calls generation and death as development and diminution rather than absolute creation and destruction. The organism changes, but its underlying unity persists. This provides a striking metaphysical context for the Christian resurrection of the dead: radical changes in corporeal condition need not entail the destruction of the individual itself.

Personhood, however, should not be confused with function. An individual's capacities and level of functioning may change over time, while the individual's spirit or soul remains a perfect unity. I therefore do not define personhood in terms of any observable capacity, such as reason, memory, or even the ability to love. Personhood is ontological: a person is an individual whose governing monad is a soul or spirit.

Works Cited

Cavallo, Andrew M. "On Mario Bunge's Definition of System and System Boundary." Science & Education 21 (2012): 1595–1599.

Cavallo, Andrew M. Gödel's God Theorem. 2020.

Leibniz, Gottfried Wilhelm. Monadology. 1714.