From the proposition 'it may not be' or 'it is contingent that

it should not be' it follows that it is not necessary that it should

not be and that it is not impossible that it should not be. From the

proposition 'it cannot be' or 'it is not contingent' it follows that

it is necessary that it should not be and that it is impossible that

it should be. From the proposition 'it cannot not be' or 'it is not

contingent that it should not be' it follows that it is necessary that

it should be and that it is impossible that it should not be.

Let us consider these statements by the help of a table:



A. B.

It may be. It cannot be.

It is contingent. It is not contingent.

It is not impossible It is impossible that it

that it should be. should be.

It is not necessary It is necessary that it

that it should be. should not be.



C. D.

It may not be. It cannot not be.

It is contingent that it It is not contingent that

should not be. it should not be.

It is not impossible It is impossible thatit

that it should not be. should not be.

It is not necessary that It is necessary that it

it should not be. should be.



Now the propositions 'it is impossible that it should be' and 'it is

not impossible that it should be' are consequent upon the propositions

'it may be', 'it is contingent', and 'it cannot be', 'it is not

contingent', the contradictories upon the contradictories. But there

is inversion. The negative of the proposition 'it is impossible' is