Hume introduces two types of statements: demonstrative and probable, and this is where we begin to find our problem of induction. A demonstrative statement is one whose truth or falsity is self-evident. This is the case for mathematical and logical statements; for example, the statement “2+2=4” is self-evidently true and cannot be denied. To deny that 2+2=4 is to fail to understand what is meant by “2”, “4”, “+”, “=“. Similarly, “all bachelors are unmarried” or “all triangles are three-sided” are also self-evidently true and cannot be denied.