DIAGRAM
1

R. Ishmael’s Rule No. 1,
concerning a-fortiori argument, can be represented by a triangular
star
, at the center of which is the middle item (R) through which the three
other items, P, Q, and S are related to each other.



Diagram 1a

The a-fortiori
argument may also be represented, with reference to the comparative propositions
that underlie it, as ordering items P, Q, and S, according to their position in
a common continuum R:




Diagram
1b


This diagram is based on the following syllogisms:

Figure
1

Figure
2

Figure
3

Figure
4

Rp
> Rq

Rp
> Rq

Rp
> Rq

Rp
> Rq

Rq
> Rs

Rp < Rs

Rs > Rp

Rs < Rq

So, Rp >
Rs

So, Rq <
Rs

So, Rs >
Rq

So, Rs <
Rp

Note that the four figures of a-fortiori should not be confused with the
four of syllogism they imply, which are, in the order shown: the fourth, third,
first and second figures.