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.

BA_rb_A_r_A, CE_l_A_r_E_nt_, DA_r_II, FE_r_IO_que_ prioris;
CE_s_A_r_E, CA_m_E_str_E_s_, FE_st_I_n_O, BA_r_O_k_O, secundae;
Tertia DA_r_A_pt_I, DI_s_A_m_I_s_, DA_t_I_s_I, FE_l_A_pt_O_n_,
BO_k_A_rd_O, FE_r_I_s_O_que_, habet; quarta insuper addit,
B_r_A_m_A_nt_IP, CA_m_E_n_E_s_, DI_m_A_r_I_s_, FE_s_A_p_O,
F_r_E_s_I_s_O_n_.

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
SM

FE_st_I_n_O is written--

No P is in M.
Some S is in M.
Some S is not in P.

The Fourth Figure being

PM
MS

DI_m_A_r_I_s_ is

Some P is in M.
All M is in S.
Some S is in P.

The initial letter in a Minor Mood indicates that Mood of the First to
which it may be reduced. Thus Festino is reduced to Ferio, and Dimaris
to Darii. In the cases of Baroko and Bokardo, B indicates that you
may employ Barbara to bring any impugner to confusion, as shall be
afterwards explained.

The letters _s_, _m_, and _p_ are also significant. Placed after a
vowel, _s_ indicates that the proposition has to be simply converted.
Thus, FE_st_I_n_O:--

No P is in M.
Some S is in M.
Some S is not in P.

Simply convert the Major Premiss, and you get FE_r_IO, of the First.

No M is in P.
Some S is in M.
Some S is not in P.

_m_ (_muta_, or _move_) indicates that the premisses have to be
transposed. Thus, in CA_m_E_str_E_s_, you have to transpose the
premisses, as well as simply convert the Minor Premiss before reaching
the figure of CE_l_A_r_E_nt_.

All P is in M No M is in S
=
No S is in M All P is in M.

From this it follows in CE_l_A_r_E_nt_ that No P is in S, and this
simply converted yields No S is in P.

A simple transposition of the premisses in DI_m_A_r_I_s_ of the Fourth

Some P is in M
All M is in S

yields the premisses of DA_r_II

All M is in S
Some P is in M,

but the conclusion Some P is in S has to be simply converted.

Placed after a vowel, _p_ indicates that the proposition has to be
converted _per accidens_