Evaluation of Argument Based on Reason

Analytic vs Synthetic Arguments

Analytic arguments are tautological, their truth is self-contained. An example is ‘all bachelors are unmarried men’.
Synthetic arguments are derived from evidence outside themselves. They might be true, but to know whether they are true we require external evidence.

Based on reason alone, Anselm’s Ontological Argument proposes that if it is possible to conceive of a perfect being, then it must exist. This is an example of an analytic argument and has prompted debate.
Descartes’ Ontological Argument suggests the idea of God necessarily includes existence, thus God must exist. Like Anselm’s, this argument is analytic.
Kant criticised these arguments, stating that existence is not a real predicate or characteristic, so you can’t define something into existence.

Kant’s Moral Argument suggests that the existence of morality points towards the existence of God, stating that moral law implies a moral lawgiver.
However, some argue that morality can exist independently from a deity, for instance through evolution or as products of society.

These arguments are both examples of synthetic arguments.
The Cosmological Argument, for example, uses the existence of the universe to argue for a cause or a ‘necessary being’, God. Thomas Aquinas and Leibniz are key contributors to this argument.
The Teleological Argument, or argument from design, asserts that the order and complexity witnessed in the world indicate a designer. Famous proponents of this argument include Paley and Swinburne.