Knowing is wanted for itself
Aristotle argues that humans by nature desire to know. The evidence is that we enjoy our senses even when they serve no use. Sight is prized most because it brings to light the most differences between things.
Philosophy
Aristotle examines being, substance, causation and first principles in the collection later called Metaphysics.
'To be' has one primary sense
Things are said 'to be' in several ways, such as being a quality or a quantity. Aristotle argues that one sense is primary: what a thing is. So the question 'what is being?' becomes the question 'what is substance?'.
Craft grows from repeated experience
Sensation produces memory in some animals, and many memories build up experience. Craft knowledge appears when many experiences yield one general judgement about a whole class of cases. Other animals live mostly by appearances and memories, while humans also live by craft and reasoning.
The highest knowledge serves no purpose
The most truly philosophical sciences are pursued for their own sake, not for practical advantage. Wisdom, on this view, is knowledge of first causes and principles, so seeking it means asking what kinds of causes those are.
A science of being as such
Aristotle proposes a 'first philosophy' that studies being simply as being, not any one kind of thing. This separates it from sciences that each cover a single domain. It looks behind the study of nature, because a changing natural world is ordered but cannot explain itself.
Raw matter cannot be substance
Strip away every property of a thing and what remains is bare matter that is in itself nothing definite. Aristotle argues that substance must be separable and a definite 'this'. So form, and the combination of form and matter, count as substance more than matter does.
Four rival candidates for substance
To find what a thing's substance is, Aristotle tests four options in turn: its essence, the universal, the genus, and the underlying subject. Commentators argue that the resulting commitments may not all fit together consistently, and the tension is still debated.
Form is activity within material
On one reading, form is not just an arrangement of parts but a being-at-work inside material. Being is then closest to active functioning, not static structure. This ties Aristotle's account of what things are to his account of how they change and exist.
Motion needs an unmoved source
Aristotle argues that change cannot go back without end. There must be an eternal, unchanging substance that causes motion without being moved itself. Everything that exists and changes depends on this first principle.