A syllogism is an argument, a chain of reasoning, first articulated by Aristotle, the father of logic. It consists of three propositions or premises. The first proposition is the major premise (MP); the second the minor (mp), and the third is the conclusion (C). If the argument is constructed properly and the premises are true, then the conclusion is conclusive, not just probable.
The reliability of the conclusion derives from the syllogism’s middle term. The middle term links the major and minor premises together. For example: All men are mortal (MP), Socrates is a man (mp), therefore, Socrates is mortal (C). The middle term is men and man respectively. Since Socrates is a man, he is in the category of men, all of which are mortal, so the conclusion necessarily follows from the truth of the major and minor premises.
The syllogism plays an important role in morality; it leads us to knowledge of the correct choice of action, the morally good thought, word, or deed we ought to take in our everyday lives to reach our eternal destiny: the Beatific Vision. Our conscience is a judgement of reason; it is a syllogism working to show us the good and avoid evil. It functions like this: the major premise is the general, universal moral law; the minor premise is more specific and pertains to a concrete situation calling for a choice; the conclusion is the morally correct choice. For example, we may be tempted to shoplift a candy bar, but our conscience tells us, in the following manner, that this is wrong: I must do good and avoid evil (MP), stealing is forbidden by the seventh commandment (mp); therefore, I must not shoplift the candy bar. (C)
Our conscience functions by “applying a general principle to a particular case by an automatic syllogism.” The syllogism reflects the wonderful reasoning program God has implanted in us to lead us to Him.