All human life is dependent on vegetation._ Or again: _All men are living creatures; Socrates is a man; .'.

Socrates is a living creature._ The decision of this issue turns upon the question (_cf._ chap.vi.Sec.

3) how far a Logician is entitled to assume that the terms he uses are understood, and that the identities involved in their meanings will be recognised.

And to this question, for the sake of consistency, one of two answers is required; failing which, there remains the rule of thumb.
First, it may be held that no terms are understood except those that are defined in expounding the science, such as 'genus' and 'species,' 'connotation' and 'denotation.' But very few Logicians observe this limitation; few would hesitate to substitute 'not wise' for 'foolish.' Yet by what right?
Malvolio being foolish, to prove that he is not-wise, we may construct the following syllogism: _Foolish is not-wise; Malvolio is foolish; .'.

Malvolio is not-wise._ Is this necessary?
Why not?
Secondly, it may be held that all terms may be assumed as understood unless a definition is challenged.