Footnote 1

The term "idea" here is used to represent all pure form. This includes symbols, mathematics, software, descriptions, and informational content, abstract or otherwise. We know from computational theory that every idea can be encoded in a string of atomic symbols. For example, the idea of a square, either the general idea of a square or of a specific square can be represented as a set of edges which in turn can be represented as a set of points which can then be represented by a set of cartesian coordinates which can be represented as a binary string. Hence, the set of all ideas has an equivalent representation as a set of strings. The set of all possible strings represents all possible ideas.

When we mentally acquire an idea, we can obtain it either from someone else (by discussion, etc.), by reading about it, or by originating it ourselves by mental construction. In all cases, to store, remember, or communicate the idea requires that the idea be physically encoded, either in sound waves in the air, text in a book, magnetic states on a disk, by electro-chemical states in a brain, or by some other physical means.