The principle of identity—This is the law of necessary truth and non-contradiction. A is A and never not-A. The opposite of a necessary truth is a contradiction.

The principle of the best—A contingent truth can have an opposite that is not a contradiction. God, who is perfectly wise, good, and powerful did not have to create the world. But he chose to do so and because He chose it, it is the best possible world.

The principle of sufficient reason—Everything that exists or occurs must have a reason that was sufficient to bring it about.

Metaphysically necessary principles—Leibniz had a number of these, which included: everything possible demands to exist and it will exist unless prevented; activity is essential to substance; and states of things remain unless or until there is a reason for them to change.

Principles of order—These consisted of three laws of order: the law of continuity, the law that every action involves a reaction, and the law that cause and effect are equal.

Efficient and final causation—Efficient causes are what immediately make things happen, whereas final causes are the ends or goals of higher substances. The entire realm of efficient causation is designed to serve the realm of final causation.

Principle of the natural—Everything that God allows to exist and happen, he chooses from what is natural; otherwise He would constantly be performing miracles. What is natural is always in between what is essential or necessary and what is accidental.