1.2.5 True and False

In Scheme, the boolean values true and false are denoted by #t and #f. However, any Scheme value can be treated as a boolean for the purpose of a conditional test. This manual uses the word true to refer to any Scheme value that counts as true, and the word false to refer to any Scheme value that counts as false. In conditional tests, all values count as true except for #f, which counts as false (see Conditionals).