| Common salt is sodium chloride, | (1) |
| Sodium chloride crystallizes in a cubical form, | (2) |
| What crystallizes in a cubical form does not possess the power of double refraction; | (3) |
it will follow that
| Common salt does not possess the power of double refraction. | (4) |
Taking our letter-terms thus,
A = Common salt,
B = Sodium chloride,
C = Crystallizing in a cubical form,
D = Possessing the power of double refraction,
we may state the premises in the forms
| A = B, | (1) |
| B = BC, | (2) |
| C = Cd. | (3) |
Substituting by (3) in (2) and then by (2) as thus altered in (1) we obtain
| A = BCd, | (4) |
which is a more precise version of the common conclusion.