I also came to see that liberalism's superficial optimism concerning human nature caused it to overlook the fact that reason is darkened by sin. The more I thought about human nature the more I saw how our tragic inclination for sin causes us to use our minds to rationalize our actions. Liberalism failed to see that reason by itself is little more than an instrument to justify man's defensive ways of thinking. Reason, devoid of the purifying power of faith, can never free itself from distortions and rationalizations.