anthropic principle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various hypotheses in theoretical physics asserting that human existence and the ability to observe the universe are necessary rather than contingent facts about the universe and must be considered when interpreting or theoretically constraining fundamental physical laws.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of several similar explanations for the nature of the universe, and for the values of its fundamental constants, that states either that the universe is as it is because otherwise we wouldn't be here to observe it, or that the very presence of intelligent life constrains the universe to be as it is.