Transcript: Deduction is a way of combining observations or statements made in science logically. Deduction provides a very strong way of connecting observations with a conclusion. Typically we start with premises and combine them to draw conclusions. For example, if based on measurement I decided that the sun is larger then the Earth and independently that the Earth is larger then the moon, I could deductively conclude that the sun is larger then the moon. In a sense deduction contains no more information then is provided in the two statements, but it’s a powerful and watertight way of combining different pieces of information. It does however depend on the premises being correct. If either premise is wrong the conclusion is invalid. Arithmetic is an example of a deductive system, and we can see that deduction is powerful and watertight. The statement 2 + 2 = 4 does not apply just on Fridays or when there is a “y” in the month. It is true always and forever. It is a part of the apparatus of arithmetic.