[31] Hist. Ind. Sc. i. 52.
[32] Nov. Org. Aph. 60.
[33] "An advocate," says Mr. De Morgan (Formal Logic, p. 270), "is sometimes guilty of the argument à dicto secundum quid ad dictum simpliciter: it is his business to do for his client all that his client might honestly do for himself. Is not the word in italics frequently omitted? Might any man honestly try to do for himself all that counsel frequently try to do for him? We are often reminded of the two men who stole the leg of mutton; one could swear he had not got it, the other that he had not taken it. The counsel is doing his duty by his client, the client has left the matter to his counsel. Between the unexecuted intention of the client, and the unintended execution of the counsel, there may be a wrong done, and, if we are to believe the usual maxims, no wrong-doer."
The same writer justly remarks (p. 251) that there is a converse fallacy, à dicto simpliciter ad dictum secundum quid, called by the scholastic logicians, fallacia accidentis; and another which may be called à dicto secundum quid ad dictum secundum alterum quid (p. 265). For apt instances of both, I must refer the reader to Mr. De Morgan's able chapter on Fallacies.
[34] An example of this fallacy is the popular error that strong drink must be a cause of strength. There is here fallacy within fallacy; for granting that the words "strong" and "strength" were not (as they are) applied in a totally different sense to fermented liquors and to the human body, there would still be involved the error of supposing that an effect must be like its cause; that the conditions of a phenomenon are likely to resemble the phenomenon itself; which we have already treated of as an à priori fallacy of the first rank. As well might it be supposed that a strong poison will make the person who takes it, strong.
[35] In his later editions, Archbishop Whately confines the name of Petitio Principii "to those cases in which one of the premises either is manifestly the same in sense with the conclusion, or is actually proved from it, or is such as the persons you are addressing are not likely to know, or to admit, except as an inference from the conclusion: as, e.g. if any one should infer the authenticity of a certain history, from its recording such and such facts, the reality of which rests on the evidence of that history."
[36] No longer even a probable hypothesis, since the establishment of the atomic theory; it being now certain that the integral particles of different substances gravitate unequally. It is true that these particles, though real minima for the purposes of chemical combination, may not be the ultimate particles of the substance; and this doubt alone renders the hypothesis admissible, even as an hypothesis.
[37] Hist. Ind. Sc. i. 34.
[38] "And coxcombs vanquish Berkeley with a grin."