| Fig. iv. | = | Fig. i. |
| No P is in M | No M is in P | |
| All M is in S | Some S is in M. |
It can be demonstrated (we shall see presently how) that altogether there are possible four valid forms or moods of the Second Figure, six of the Third, and five of the Fourth. An ingenious Mnemonic of these various moods and their reduction to the First Figure by the transposition of terms and premisses has come down from the thirteenth century. The first line names the moods of the First, Normal, or Standard Figure.
BArbArA, CElArEnt, DArII, FErIOque prioris;
CEsArE, CAmEstrEs, FEstInO, BArOkO, secundæ;
Tertia DArAptI, DIsAmIs, DAtIsI, FElAptOn,
BOkArdO, FErIsOque, habet; quarta insuper addit,
BrAmAntIP, CAmEnEs, DImArIs, FEsApO, FrEsIsOn.
The vowels in the names of the Moods indicate the propositions of the Syllogism in the four forms, A E I O. To write out any Mood at length you have only to remember the Figure, and transcribe the propositions in the order of Major Premiss, Minor Premiss, and Conclusion. Thus, the Second Figure being
PM