It is only when a decision has to be taken affecting the more distant purposes of his life that the man enters on a region of definitely rational thought where the dog cannot follow him, in which he uses words, and is more or less conscious of his own logical methods.
But the weakness of inference by automatic association as an instrument of thought consists in the fact that either of a pair of associated ideas may call up the other without reference to their logical connection.

The effect calls up the cause as freely as the cause calls up the effect.

A patient under a hypnotic trance is wonderfully rapid and fertile in drawing inferences, but he hunts the scent backward as easily as he does forward.

Put a dagger in his hand and he believes that he has committed a murder.

The sight of an empty plate convinces him that he has had dinner.