Emptiness and Objects

[Tiff]

Since nothing was recorded in writing by Gautama himself during his lifetime, the task of narrowing down what is attributed to his teachings is an inscrutable one.
Nonetheless, here is the Wiki page on Buddhist Philosophy:
Buddhist philosophy deals extensively with problems in metaphysics, phenomenology, ethics, and epistemology.

Some scholars assert that early Buddhist philosophy did not engage in ontological or metaphysical speculation, but was based instead on empirical evidence gained by the sense organs (ayatana).[1] Buddha is said to have assumed an unsympathetic attitude toward speculative thought in general.[2] A basic idea of the Buddha is that the world must be thought of in procedural terms, not in terms of things or substances.[3] The Buddha advised viewing reality as consisting of dependently originated phenomena; Buddhists view this approach to experience as avoiding the two extremes of reification and nihilism.[4] Nevertheless, Buddhist scholars have addressed ontological and metaphysical issues subsequently.


And later...

Early development
Certain basic teachings appear in many places throughout the early
texts, so most scholars conclude that the Buddha must at least have
taught something of the kind:[12]
the three characteristicsthe five aggregatesdependent arisingkarma and rebirththe four noble truthsthe eightfold pathnirvanahttp://en.wikipedia.org/wiki/Buddhist_philosophy