The Cornerstone is the first stone set in place, determining the alignment, strength, and integrity of everything built upon it. Throughout history, builders have examined stones for beauty or convenience, often discarding the one that appeared least impressive—only to discover later that it was the only stone capable of bearing the full weight of the structure. In the same way, history records a figure rejected by religious authorities, political powers, and cultural elites, yet proven indispensable as the true measure of truth, sacrifice, and redemption. This cornerstone was not chosen by human preference but established by divine intent, revealing that foundations fail not from effort alone, but from being set on the wrong reference point. Here, we uncover why Christ stands as the rightful Cornerstone—rejected, tested, and vindicated—upon whom every enduring life, philosophy, and civilization must ultimately be aligned.