Morris Raphael Cohen

Liberalism, on the other hand, regards life as an adventure in which we must take risks in new situations, in which there is no guarantee that the new will always be the good or the true, in which progress is a precarious achievement rather than inevitability.

Liberalism is an attitude rather than a set of dogmas - an attitude that insists upon questioning all plausible and self-evident propositions, seeking not to reject them but to find out what evidence there is to support them rather than their possible alternatives.