God graciously reveals how he is to all people up to the absolute greatest quantity they can perceive and understand without becoming more like him than they already are. God can reveal a great deal about himself, even to those who do not know him at all or believe in him at all, because everything in life testifies of how he is, whether the individual recognizes it or not.
We are all endowed by our Creator with a great deal of internal light, including the ability to assess the relative value of different actions we can take in decisions big and small. Like a seedling sprouting of its own accord, we can progress a great deal in our character through feeding off our internal resources. A great deal of progress is possible even in an individual that does not know or believe anything about God if they choose the best they know of, according to their understanding of what is good. This includes doing their best in every aspect of their life from the seemingly mundane to the explicitly religious and everything in between. Unfortunately, even among the religious, few people apply this latent capability with enough fervor to reach the end of its utility. Instead, they are content doing less than the best they imagine, at least in some situations, cutting themselves off from anything still better.