Postulate

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A postulate (also sometimes called an axiom) is a statement that is agreed by everyone to be correct. This is useful for creating proofs in mathematics and science, and postulates are often the basic truth of a much larger theory or law.

Postulates themselves cannot be proven, but since they are usually obviously correct this is not a problem. Here is a good example of a postulate (given by Euclid in his studies about geometry).

Two points determine (make) a line.

Using this postulate and four others like it, Euclid brought a new understanding of geometry to the world, and many people think they are some of the most influential works in geometry even now.

Sometimes postulates are not obviously correct, but are required for their consequences. The easiest case must be with Albert Einstein's postulate that the universe is homogenous. This type of postulate was necessary to make possible some major scientific achievements, but can also be problematic since not self-evident.

There are also a few characteristics that all postulates should have.

  1. They should be obvious and easy to understand, and should not have too many words that are difficult to explain.
  2. There should not be very many of them.
  3. They should all work together without making any strange results (they should be consistent).
  4. They should also be true when they are alone (so they can be used independently).

Postulates are sometimes proved to be wrong after they have been known for a long time, but this is usually because something new has been discovered, and the original creator could not have known any better.