If the statement 'All human beings are mortal' is given as true, which of the following can be inferred to be true?

ASome human beings are mortal ✓ Correct

BNo mortals are non-human beings

CSome non-mortals are human beings

DSome non-human beings are not mortal

Correct answer: (A) Some human beings are mortal

Explanation

From a true universal affirmative the corresponding particular affirmative follows.

'All human beings are mortal' is an A proposition asserting the whole class.

By subalternation, whatever holds of all members holds of some members.

Hence 'Some human beings are mortal,' the I proposition, must also be true.

Subalternation from A to I is the valid immediate inference here.

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