If, then, we give the name of healthy-mindedness to the tendency which looks on all things and sees that they are good, we find that we must distinguish between a more involuntary and a more voluntary or systematic way of being healthy-minded. In its involuntary variety, healthy-mindedness is a way of feeling happy about things immediately. In its systematical variety, it is an abstract way of conceiving things as good. Every abstract way of conceiving things selects some one aspect of them as their essence for the time being, and disregards the other aspects. Systematic healthy-mindedness,
conceiving good as the essential and universal aspect of being, deliberately excludes evil from its field of vision; and although, when thus nakedly stated, this might seem a difficult feat to perform for one who is intellectually sincere with himself and honest about facts, a little reflection shows that the situation is too complex to lie open to so simple a criticism.
–William James, The Varieties of Religious Experience