§ 504. When A and O have been permuted, they become respectively E and I, and, in this form, admit of simple conversion. We have here two steps of inference: but the process may be performed at a single stroke, and is then known as Conversion by Negation. Thus from 'All A is B' we may infer 'No not-B is A,' and again from 'Some A is not B' we may infer 'Some not-B is A.' The nature of these inferences will be seen better in concrete examples. § 505. (A) All poets are imaginative. .'. No unimaginative persons are poets (E). (O) Some parsons are not clerical. .'. Some unclerical persons are parsons (I). § 506. The above inferences, when analysed, will be found to resolve themselves into two steps, namely, (1) Permutation. (2) Simple Conversion. (A) All A is B. .'. No A is not-B (by permutation). .'. No not-B is A (by simple conversion). (O) Some A is not B. .'. Some A is not-B (by permutation). .'. Some not-B is A (by simple conversion). § 507. The term conversion by negation has been arbitrarily limited to the exact inferential procedure of permutation followed by simple conversion. Hence it necessarily applies only to A and 0 propositions, since these when permuted become E and 1, which admit of simple conversion; whereas E and 1 themselves are permuted into A and 0, which do not. There seems to be no good reason, however, why the term 'conversion by negation' should be thus restricted in its meaning; instead of being extended to the combination of permutation with conversion, no matter in what order the two processes may be performed. If this is not done, inferences quite as legitimate as those which pass under the title of conversion by negation are left without a name. § 508. From E and 1 inferences may be elicited as follows-- (E) No A is B. .'. All B is not-A (A). (I) Some A is B. .'. Some B is not not-A (O). (E) No good actions are unbecoming. .'. All unbecoming actions are not-good (A). (I) Some poetical persons are logicians. .'. Some logicians are not unpoetical (O). Or, taking a privative term for our subject, Some unpractical persons are statesmen. .'. Some statesmen are not practical. § 509. When the inferences just given are analysed, it will be found that the process of simple conversion precedes that of permutation. § 510. In the case of the E proposition a compound inference can be drawn even in the original order of the processes, No A is B. .'. Some not-B is A. No one who employs bribery is honest. .'. Some dishonest men employ bribery. The inference here, it must be remembered, does not refer to matter of fact, but means that one of the possible forms of dishonesty among men is that of employing bribery. § 511. If we analyse the preceding, we find that the second step is conversion by limitation. No A is B. .'. All A is not-B (by permutation). .'. Some not-B is A (by conversion per accidens).