First:

This consequence is binding upon you regarding different qualities that can coexist, such as taste, colour, and smell. Say, then, that they are a single thing, just as knowledge, will, and power, and demand, statement, command, and prohibition, are a single thing.

Second:

It may be said that letters are mutually opposed in the same way as the meanings of speech or movements, not in the same way as blackness and whiteness.

A single locus cannot accommodate two movements or two meanings, so it cannot accommodate two letters or two sounds. There is a difference between things that are mutually opposed in themselves and things that are mutually opposed because their locus cannot accommodate them both.

If this is so, the mutual opposition of letters and movements is like the mutual opposition of the meanings of speech.

The human heart is unable to bring together all the meanings of speech at any one time. It is therefore more appropriate to group the letters of speech with their causes—namely, movements—and with their contents and significations—namely, meanings—than to group them with things that are mutually opposed in themselves, such as blackness and whiteness.

If, then, you make the meanings of speech a single thing, make its letters a single thing as well. Otherwise, what is the difference?

One might distinguish between them by saying:

Letters are segments of sounds, and sounds depend upon their causes, namely movements.

Movements are either identical or different. Both different and identical movements are mutually opposed; it is impossible for