This question asks how much plurality belongs at the most basic level of reality, and it can be counted in two ways: by individual substances and by fundamental kinds. Spinoza admits one self-sufficient substance, God or Nature, with finite things as its modes. Cartesian substance dualism admits thinking and extended substances as two irreducible kinds. Leibniz instead makes the world rest on infinitely many substances of a single kind: simple, unextended monads.
Metaphysics
How Many Fundamental Substances?
How many fundamental substances does reality contain, and of how many kinds?
Positions
- Leibnizian Substance Pluralism
Reality contains infinitely many simple, unextended substances—monads—and bodies are grounded in them rather than being substances of a second material kind.
- Spinozistic Substance Monism
Exactly one substance exists: God or Nature; every finite thing is a mode of that substance.
Held by Spinozism
- Substance Dualism
Mind and body are fundamentally distinct substances, and the mind is not reducible to the physical body.
On this question, substance dualism counts two fundamental kinds of created substance—thinking minds and extended bodies—rather than only two individual substances.
Engaged by schools of thought
- Atomism
As Aristotle reports them, Leucippus and Democritus answered with infinitely many substances of one kind: indivisible atoms of a single uniform stuff, differing only in shape, arrangement and position. Beside them is the void, which they called 'what is not' yet held to be no less real than what is. Everything else is the atoms' arrangement.
- Milesians
Thales, Anaximander, and Anaximenes each proposed one originating stuff, water, the boundless, or air, from which everything else arises. Aristotle read these as the earliest answers, each naming one basic substance, though whether the Milesians held that stuff to persist through every change is disputed.
- Pluralists
Empedocles answered Parmenides with four permanent roots, earth, water, air, and fire, mixed and parted by Love and Strife, and Anaxagoras with unlimited seeds of every kind ordered by Mind: many basic substances, none of which comes to be or perishes.
- Pythagoreanism
The fifth-century Pythagoreans, above all Philolaus, held that the world is fitted together from limiters and unlimiteds by a harmony, and that number is what makes anything knowable, so that ordered structure rather than any material stuff is what is basic.
Methods used to investigate this question
- Geometrical Method
The geometrical method (*more geometrico*) sets out definitions and axioms, then derives propositions in an explicit order, each demonstration resting on steps already established. Early modern philosophers took the form from Euclid and put it to work outside mathematics: Descartes arranged his arguments for God and the distinction of mind and body this way in the Second Replies, and Spinoza's *Ethics* carries it through an entire system.