We must content ourselves with probability in the rest: but can have no general certainty, whilst our specific idea of man contains not that real constitution which is the root wherein all his inseparable qualities are united, and from whence they flow.

Whilst our idea the word MAN stands for is only an imperfect collection of some sensible qualities and powers in him, there is no discernible connexion or repugnance between our specific idea, and the operation of either the parts of hemlock or stones upon his constitution.

There are animals that safely eat hemlock, and others that are nourished by wood and stones: but as long as we want ideas of those real constitutions of different sorts of animals whereon these and the like qualities and powers depend, we must not hope to reach certainty in universal propositions concerning them.

Those few ideas only which have a discernible connexion with our nominal essence, or any part of it, can afford us such propositions.

But these are so few, and of so little moment, that we may justly look on our certain general knowledge of substances as almost none at all.
16.