“I think, therefore I am.” – Rene Descartes.

The first stratum of reality is internal reality, that is, the reality of an individual’s mind. Rene Descartes is the prototypical example in the philosophical literature of exploration of internal reality at the elemental level. It is not surprising that as a mathematician he approaches philosophy as an attempt to find absolute truths that he can build into an indisputable understanding of reality. In his Meditations on First Philosophy, where by first philosophy he means metaphysics, he is sitting by a cozy fire in his home, and decides to doubt every belief he has ever held, even his own perceptions, and to try to identify what truth he can uncover from scratch purely by thinking.

He decides the most certain reality he can identify is his own existence – Cogito ergo sum – “I think, therefore I am.” He also notes the corollary is true: “I am a thing that thinks.” Then in an amazing contortion of thought, he decides the initial choice to doubt everything presupposes the possibility of certainty. Taken one more step, as an imperfect being, he can only be aware of certainty and perfection if the idea came from a perfect being, hence there must be a God. Also as a perfect God would not deceive him, the senses are generally reliable and the world is in fact real. But he determines that the mind’s knowledge of matter is limited by the imperfection of the body from which he receives impressions of external reality and error is unavoidable given his finite intellect within an infinite will.1

The consequence of Descartes’ line of reasoning, splitting internal concepts from external objects, results in what philosophers call dualism – reality as two parts: mind and body or immaterial and material. But this position is controversial, and many philosophers do not accept a separate status for the immaterial, believing the mind is simply the manifestation of organic processes within the physical brain. Another less common challenge to Descartes’ dualism denies the existence of the physical body and world altogether, that is, it asserts that only the immaterial is real, in which case the world is merely a projection of the mind. This position is advocated by the 18th century Irish bishop, George Berkeley (for whom the city of Berkeley, California and its University were named).2 These systems are known as monism, that is, reality as only physical or only immaterial.

(to be continued next post)

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