Ib

The ib, the heart, was for the Egyptians the seat of thought, feeling, memory, and moral character — the true center of the person, far more than the brain, which they discarded in mummification while carefully preserving the heart.

At the judgment after death, the heart was weighed in the balance against the feather of Ma'at, truth and order. If it was light — unburdened by wrongdoing — the soul passed on to blessedness; if heavy with sin, it was devoured and the person perished utterly. The 'weighing of the heart', overseen by Anubis and recorded by Thoth, made the moral life the very condition of immortality.