The surest sign that we are keeping these two commandments is, I think, that we should really be loving our neighbour; for we cannot be sure if we are loving God, although we may have good reasons for believing that we are, but we can know quite well if we are loving our neighbour. And be certain that, the farther advanced you find you are in this, the greater the love you will have for God; for so dearly does His Majesty love us that He will reward our love for our neighbour by increasing the love which we bear to Himself, and that in a thousand ways: this I cannot doubt. – St. Teresa of Avila Interior Castle, Fifth Mansions Chapter III
Anyone that has advanced at all in the faith will have no trouble loving God, at least in a cursory sense, but loving the neighbor can be much more difficult. We know the two commandments that Christ gave us, which sum up the old Law:
Jesus answered, “The first is, ‘Hear, O Israel: The Lord our God, the Lord is one; and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength.’ The second is this, ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these.” – Mark 12:29-31 (RSV2CE)
So here, Christ has reduced the old Law into its two most important parts, that is, the other parts of the Law are supposed to serve these two. St. Teresa perceives an important relation between these commandments: she does not see them as separate commandments but indeed, she sees that they are measures of each other. That is to say, one who loves his neighbor also loves God, one who loves God also loves his neighbor. However, the saint is very astute to recognize that is is difficult to measure how much we are truly loving God, but whether or not we are loving our neighbor is quite easy to measure.
This leads us to ask ourselves some truly difficult questions: If I think I love God, but have not loved my neighbor… do I truly love God? If I do not love my neighbor who I do see, how can I love the God that I cannot see?
I do not share this to cast judgment on myself nor anyone else, but St. Teresa’s quote above is one of those few that have shaken me to my core. I hope it impresses upon you as well.