It is evident from this that little “a” is the cause or the effect of little “p.” To put it in concrete form:

Let A = X number of calories of heat,

And P = 68° F., the original temperature of room,

And a = candle burning in room for ½ hour,

And p = 2° F.

Then

AntecedentsConsequent
X no. of cal. of heat in room= 68° F. temp. of room
X no. of cal. of heat + burning candle= 68° + 2° = 70°
X (no. of cal. of heat + burning candle) − burning candle= (68° + 2°) − 2° = 68°

As large “A” is increased and decreased by little “a” so large “P” appears to be increased and decreased by little “p.” This strongly suggests a causal connection between little “a” and little “p.”

(3) Other concrete illustrations.

Problem: To ascertain nature of sound.