Digital Companion to C. S. Peirce
1867 | On a New List of Categories | W 2:49; CP 1.547

This conception of the present in general, of IT in general, is rendered in philosophical language by the word “substance” in one of its meanings. Before any comparison or discrimination can be made between what is present, what is present must have been recognized as such, as it, and subsequently the metaphysical parts which are recognized by abstraction are attributed to this it, but the it cannot itself be made a predicate. This it is thus neither predicated of a subject, nor in a subject, and accordingly is identical with the conception of substance.

1887-1888 | A Guess at the Riddle | W 6:210 n. 2; CP 1.414 n.

I use substance […] in the old sense of a thing, not in the modern chemical sense.

1906 | The Basis of Pragmaticism | EP 2:394; CP 5.448 n.

…whenever we speak of a predicate we are representing a thought as a thing, as a substantia, since the concepts of substance and subject are one, its concomitants only being different in the two cases.

1910 | The Rationale of Reason | MS [R] 659:38

…one may start with the concept of a thing, a concept which can be actualized independently of anything else to which it should appertain. Such a thing in the language of philosophy is called a substance. This is in fact the proper meaning of that word which it was framed to express and what the chemists call a “substance” ought to be called a chemens (pl. chementia).