Read this week's lectionary readings here.
20 He who does not love his brother whom he has seen cannot love God whom he has not seen.
Interesting comment from (presumably) the same author who recorded this:
Jesus said to him, "Have you believed because you have seen me? Blessed are those who have not seen and yet have believed."
In practice, Christianity works. The Gospel serves the seen brother. The Gospel requires us to do for others as we would have them do for us. Wash their feet, feed them, clothe them, care for them. Listen to them, respect them, seek to understand them (because we all seek to be understood) even when we think they are wrong (because we all want people who disagree with us to be fair and respectful to our differing point of view). Love is action. Do we merely say we love, or do we actually do loving things? "Little children, let us not love in word or talk but in deed and in truth." (I John 3:18)