The Heart (Ib) — Seat of Thought & Conscience
For Egyptians, you thought with your heart — and it was your heart that testified when you died.
Also: heart · ib · jb · haty · seat of mind · heart as conscience · heart amulet · heart scarab · spell 30
Egyptians located the mind in the heart, not the head: the heart (ib) was the seat of thought, feeling, will, memory, and conscience. Wisdom texts speak of guiding or following one's heart; the creator Ptah was said to conceive creation in his heart. Because the heart held the record of one's deeds, it was the heart that was weighed at the judgment — and amulets and spells were provided to keep it from betraying its owner.
In short
The Egyptian conception of the heart (ib) as the center of thought, emotion, intention, memory, and moral character — the organ that plans and decides, and that testifies for or against a person at the judgment.
Where it’s found
Wisdom literature; the Memphite Theology; Book of the Dead heart spells
How the idea developed across Egypt
The heart-as-mind conception is constant across Egyptian literature from the Old Kingdom; it underlies the Memphite 'creation by the heart's thought,' the wisdom texts' counsel about the heart, and Book of the Dead 'heart spells' (e.g. spell 30) that protect the heart at judgment.
Egyptian uses two heart-words (ib and haty) with overlapping senses; do not over-systematize the distinction.