Again, neither can you arrive at the definition of a given subject, by assuming in general terms what a definition ought to be, and then declaring a given form of words to be conformable to such assumption; because your minor premiss must involve _Petitio Principii_. The same logical fault will be committed, if you take your departure from an hypothesis in which you postulate the definition of a certain subject, and then declare inferentially what the definition of its contrary must be. The definition which you here assume requires proof as much as that which you infer from it.[15] Moreover, neither by this process, nor by that of generic subdivision, can you show any reason why the parts of the definition should coalesce into one essential whole. If they do not thus coalesce--if they be nothing better than distinct attributes conjoined in the same subject, like _musicus_ and _grammaticus_--the real essence is not declared, and the definition is not a good one.[16] [Footnote 15: Analyt. Post. II. vi. p. 92, a. 6-28. Themist. p. 76. Rassow renders [Greek: e)x u(pothe/seôs]--"assumptâ generali definitionis notione;" and also says: "[Greek: to\ ti/ ê)=n ei)=nai]--generalem definitionis notionem; [Greek: to\ ti/ e)stin]--certam quandam definitionem, significare perspicuum est." (Aristotelis de Notionis Definitione Doctrina, p. 65).] [Footnote 16: Analyt. Post. II. vi. p. 92, a. 32. That the parts of the definition must coalesce into one unity is laid down again in the Metaphysica, Z. pp. 1037, 1038, where Aristotle makes reference to the Analytica as haying already treated the same subject, and professes an intention to complete what has been begun in the Analytica; [Greek: e)ph' o(/son e)n toi=s A)nalutikoi=s peri\ o(rismou= mê\ ei)/rêtai.]]