Aristotle

(384 – 322 BC)

Greek philosopher and polymath of the Classical period. He was a student of Plato, and spent around twenty years in his Academy. He left to Macedonia after the death of Plato and became the teacher of Alexander the Great, Ptolemy and Cassander. When he returned to Athens he founded an academy of his own – the Lyceum – where he taught students and established a library.

The principal ideas where he develops his doctrine are compiled in his most famous work, the Metaphysics. Regarding metaphysics, his main disagreement with his teacher was Plato’s other-worldliness and idealism, whereas Aristotle was more ‘down-to-earth’.

Plato held that reality was made of two: (1) the ideal world of Forms and (2) the reality we live in and perceive, which is only an imitation/reflection of the former.
Aristotle disagreed and held that there is only one world – the one we live in and perceive.According to Aristotle, there is a distinction between form and matter, but that these are two features of one reality, and can only be distinguished in thought, not in fact. So, forms are not separate entities, but they are in the world and embedded in particular things. An object or substance has both:
(1) form or essence: what an object is (it’s a chair, a book, a tree, etc.)
(2) matter: what distinguishes this particular object

Further, Aristotle makes a distinction between properties of a thing:

essential properties are those that are necessary for the thing to be what it is, without it, the thing looses its identity (for example, to possess a soul and be rational are considered essential properties of being human)
accidental properties are those that are not necessary for something to be what it is (most humans have hair, but ‘to have hair’ is not an essential property of being a human – one can also be bald and still be a human)

In order to account for change, Aristotle introduced an important distinction which reinterprets objects (both their form and matter) in terms of their potentiality and actuality:

potentiality encompasses all the possibilities that a thing can have or become, it is all that could be (for example, a tomato seed contains the potentiality of everything that it could become; the tomato plant in all its various stages of growth, as well as the tomato fruit)
actuality represents the fulfilment of a possibility, it is what is manifests or is manifested (from the above example, the tomato plant you have in your garden in its current state)

In this way, each individual substance is a self-contained teleological (goal-oriented) system. In growth and change, the essence of a substance does not change, only its accidental properties do. Further, Aristotle analysed objects and their potential to change from potentiality to actuality in terms of four causes:

material cause: the material out of which something is or can be made (pieces of wood, stone, brick and glass that could make up a house)
formal cause: that which it strives to be, the form or essence (the house that is in the architect’s mind)
efficient cause: the actual force that brings about change (the builders building the house)
final cause: the ultimate purpose of an object (to have a home)

Aristotle held that each substance is striving for self-actualization and for whatever perfection is possible within the limits of its essence. Everything in the universe is striving towards a Final Cause which has been set forth by a God-like entity, which Aristotle termed the Prime Mover.

Another important aspect of Aristotle’s work is his moral philosophy, described in his Nicomachean Ethics. He states that all human acts are directed towards happiness (eudaimonia in Greek, also translated as well-being). For Aristotle, happiness is living in accordance with virtue and in conformity with reason.