The demands that follow that promise may seem, however, to be impossible: do not let your uprightness be hypocritical; do not be angry with one another; do not turn women into sexual objects; do not abandon your wives.
Jesus sums up his commandments in two steps. First, resist evil and love your enemies. Then, be perfect, morally upright. That summation seems to underscore the impossibility of his commandments. But it does so only if we think of moral perfection as our something we achieve, a product of will.
The word teleios also has the connotation of wholeness, and Jesus' description of the Father, immediately preceding the commandment to be perfect or whole, gives us a good idea of how to understand the perfection or wholeness demanded. Jesus summarizes his demands by saying: "Be like the Father, who causes the sun to rise and rain to fall on both the just and unjust." Like our Father, our love must know no boundaries. We must be his children, repeating his love. Like Jesus and Alyosha, we must kiss softly on the lips those who would condemn us, being one with them as the Father is one with them.
It may still be tempting to think that such perfection is not only unattainable, but unendurable. But Christian perfection doesn't mean never making mistakes. It doesn't mean never sinning. In fact, the perfection commanded is one available only to those who are sinners. For it is not a perfection attainable by steeling oneself against the temptations of the world, by gritting one's teeth and lifting oneself up by the bootstraps. Christian perfection is not the result of an act of will, and thinking it is makes what passes for Christian freedom unendurable.
Instead, Christian perfection is attainable only by letting go of the person I have made myself through my supposed freedom, letting go of what I have become by seeking to fulfill desire, giving up both illusory fulfillment of desire and the murderous envy of those who seem to achieve that fulfillment.
Christian perfection is not self-perfection, but perfection attained through trust in Jesus and life in the uncertainty of what that will mean. It comes in the Kierkegaardian repetition of Jesus' kiss.
The choice, then, is not between unendurable Christian freedom and the demonic temporary fulfillment of desire. A third option is that of faith, trust that I can be delivered from myself to something better, to the loving wholeness of God. I must abide actively in that trust, waiting hopefully for the perfection and happiness that has been set before me as a promise, but remembering that I cannot make myself anything that matters. Christian freedom is the freedom of grace, not that of will. It comes in the loving submission of a child rather than in the power of a hero.
(PS: Thanks to my friends on LDS-Herm).