The Five Ways


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The ways of allegedly demonstrating the existence of God formulated by Aquinas (Summa Theologia, Ia 3. It is important in understanding the significance of these arguments to Aquinas that the entire context stretches from Ia 2 to 11). The ways are given thus:
  1. Motion is only explicable if there exists an unmoved, first mover.
  2. the chain of efficient causes demands a first cause
  3. the contingent character of existing things in the world demands a different order of existence, or in other words that something has a necessary existence.
  4. the graduations of value in things in the world require the existence of something that is most valuable, or perfect.
  5. the orderly character of events points to a final cause, or end to which all things are directed, and the existence of this end demands a being that ordained it.
All of the arguments are physico-theological arguments. The second is a first cause argument and the first is the Aristotelian variety of it that singles out the causes of motion as particularly in need of a starting-point. The third is a variety of the cosmological argument, as it had been formulated by Avicenna. The fourth is the degrees of perfection argument. The fifth is a version of the argument from design.

Physico-Theological Argument

A term used by Kant to denote any argument that starts from some fact about the world, and attempts to derive the existence of a deity.
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First Cause

One of the classic arguments for the existence of God. Every event in the natural world has a preceding cause. But this opens up a regress of causes stretching back forever in time. To stop the regress we must postulate a first cause, and this will be the creative action of God. Russell supposed this argument to be uniquely bad, in that the conclusion (that there is a first cause) actually contradicts the premise (that every event has a preceding cause). To avoid his complaint one who uses this argument must distinguish between natural events and unnatural or supernatural events. The former all require causes, but the latter may be their own cause. God is causa sui. The difficulty then lies in seeing why the natural world should not be causa sui. The argument inherits the problems of the cosmological argument, of which it is a variant.
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The Cosmological Argument

An influential argument (or family of arguments) for the existence of God. Its premises are that all natural things are dependent for their existence on something else; the totality of dependent beings must then itself depend upon a non-dependent or necessarily existent, being, which is God.

Like the argument to design, the cosmological argument was attacked by Hume and Kant. Its main problem is that it requires us to make sense of the notion of necessary existence. For if the answer to the question of why anything exists is that some other thing of a similar kind exists, the question merely arises again. So the 'God' that ends the question must exist necessarily; it must not be an entity of which the same kind of question can be raised.

The other problem with the argument is that it unfortunately affords no reason for attributing concern and care to the deity, nor for connecting the necessarily existent being it derives with human values and aspirations.


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The Degrees of Perfection Argument

The fourth of the Five Ways of Aquinas. Its premises include:
  1. some things are better and more noble than others
  2. comparative terms describe varying degrees of approximation to a superlative
  3. whatever is best is the most fully in being, or most real
  4. whenever things possess some property in common, the one most fully possessing it causes it in the others.
Hence, there is something which "causes in all other things their being, their goodness and whatever other perfections they have. And this we call God".

The argument presupposes a concept of causation as a kind of gift of reality. This idea survived until the 17th century, but is no longer attractive. In addition, the second premise is clearly faulty (one number may be greater than another, but there is no greatest number; similarly one automobile may be better than another without being a perfect automobile). In so far as the argument depends upon an association of value with degrees of reality, and thence with causation, it is probably best seen as a version of the cosmological argument.