Spelling irregularities where there was no obviously preferred version were left as is. Variants include: "alkalies" and "alkalis;" "apprise" and "apprize;" "coexistent" and "co-existent" (along with derivatives); "coextensive" and "co-extensive;" "e. g." and "e.g."; "encumbered" and "incumbered;" "formulæ" and "formulas;" "i. e." and "i.e."; "nonentity" and "non-entity;" "recal" and "recall" (and derivatives); "rectilinear" and "rectilineal;" "stopt" and "stopped."

Volume I. contains "το ὄν," while Volume II. spells it "τὸ ὄν." The spellings were left as is, in each case.

Changed "3" to "4" on page xiii: "4. —and from descriptions."

Inserted missing page number, "167," for Chapter VIII, section 7 on page xiii.

Moved the semi-colon inside the quotation marks in the footnote on page 14: "the Science of the Formal Laws of Thought;".

Changed "sub-divisions" to "subdivisions" on page 59: "three subdivisions."

Changed "pre-supposed" to "presupposed" on page 75: "they are presupposed."

In the footnote to page 122, changed the Greek character upsilon with dasia and oxia to upsilon with psili and oxia, making the transliteration "deuterai ousiai."

Changed "he" to "be" on page 189: "to which it may be reduced."

Changed "cb." to "ch." in footnote on page 227: "Theory of Reasoning, ch. iv."

Changed "reconcilable" to "reconcileable" on page 240: "not easily reconcileable."

Preserved the hyphen in "counter-acting" on page 280. Usually this is spelled without the hyphen, but this instance is in a quotation.

Moved parenthesis that was after "to" to before it on page 321: "(to return to a former example)."

Put "i.e." in italics on page 335: "i.e. by a power of some sort."

Changed "paralyzed" to "paralysed" on page 389: "nerves of motion were paralysed."