To Use or Not to Use

So I've been wondering: what should we do about all of the insightful or thought provoking quotes from those who are unbelievers? The tendency is usually to shy away from anyone's words of wisdom if the person is not a Christian. Is this really the right approach, though? After all, Gandhi, Nietzsche, Camus, and every other human who ever said something of value was created in God's image. In my mind, it's part of common grace - the ability to say something notable, worth listening to - whether or not you're a Christian. Now this doesn't mean we should hang upon their every word and accept whatever they say - common sense can tell you that. The farther something comes from the Bible, the more it must be taken with a grain of salt. But I think the fear of listening to what these people have to say just because they're unbelievers is an area Christians need to grow in. God can use unusual sources to teach us, and I think if we measure what we hear with what is taught in the Bible, and we remember God's promise that He will not lead us astray, that we may find gold in unusual places.