P₁ — A B C D
P₂ — A D E F
P₃ — A L M N
P₄ — A O P Q
In the first case, the sole invariable antecedent is A, and, therefore, we infer that A is probably the cause of P. In the second case, the invariable consequent being A, is probably the effect of P.
(3) Concrete examples illustrating first statement.
The Problem: Cause of John’s tardiness.
On investigation the various antecedents are these: (1) John has his breakfast at seven; (2) after breakfast he carries his father’s dinner to him and (3) feeds the hens; and then (4) goes to school by the path through the woods and around the mill pond.
Phenomenon as a consequent. John is tardy. Determining to do away with the tardiness, the teacher brings about a variation in the antecedents, varying one at a time taken in the order indicated above.
To wit: (1) Varying the first antecedent.