Prior Analytics - Book II   

reference to each of the two middle terms: e.g. that A belongs to

all B, but to no C, and both B and C belong to all D. For it turns out

that the first premiss of the one syllogism is either wholly or

partially contrary to the first premiss of the other. For if he thinks

that A belongs to everything to which B belongs, and he knows that B

belongs to D, then he knows that A belongs to D. Consequently if again

he thinks that A belongs to nothing to which C belongs, he thinks that

A does not belong to some of that to which B belongs; but if he thinks

that A belongs to everything to which B belongs, and again thinks that

A does not belong to some of that to which B belongs, these beliefs

are wholly or partially contrary. In this way then it is not

possible to think; but nothing prevents a man thinking one premiss

of each syllogism of both premisses of one of the two syllogisms: e.g.

A belongs to all B, and B to D, and again A belongs to no C. An

error of this kind is similar to the error into which we fall

concerning particulars: e.g. if A belongs to all B, and B to all C,

A will belong to all C. If then a man knows that A belongs to

everything to which B belongs, he knows that A belongs to C. But

nothing prevents his being ignorant that C exists; e.g. let A stand

for two right angles, B for triangle, C for a particular diagram of

a triangle. A man might think that C did not exist, though he knew

that every triangle contains two right angles; consequently he will

know and not know the same thing at the same time. For the

expression 'to know that every triangle has its angles equal to two

right angles' is ambiguous, meaning to have the knowledge either of

the universal or of the particulars. Thus then he knows that C

contains two right angles with a knowledge of the universal, but not

with a knowledge of the particulars; consequently his knowledge will

not be contrary to his ignorance. The argument in the Meno that

learning is recollection may be criticized in a similar way. For it

never happens that a man starts with a foreknowledge of the

particular, but along with the process of being led to see the general