The fundamental tenet of Christianity?

Question received today:

What is the most fundamental tenet of Christianity? Is it self salvation or service to others?

Our answer:

From a Catholic perspective, we would probably say the fundamental tenet of Christianity is Love. God is Love, so to truly Love is to embrace God. One cannot be close to God and not saved, and one cannot be close to God without being of service to others. Everything good comes from God; everything good comes from Love.

According to Frank Sheed, a great Catholic writer, we believe we are
saved in community, so the two options, self salvation and service to
others (the two greatest commandments), are inseparable.

John Donne’s Meditation 17 reflects this as well. We are together in this life.

When we look for a rule-based religion, we miss the point. Rules are simple and absolve us of the need to think, and they remove the need to truly love others. If God had wanted us to be fundamentally about rules, Jesus need not have lived among us, suffered, died, and rose. In the readings during the day today, we see Peter and John hurrying to the empty tomb, but John outran Peter. Once again, the last shall be first. John followed the rules, and did not enter the tomb. It would have made him unclean, and it was against the rules. When Peter arrived, he rushed in, as Love drove him to do. When John saw this, he entered, and believed.

The fundmental tenet of Christianity is Love. If we miss that, none of the rest matters.