Duties of the Heart, First Treatise on Unity 1/חובות הלבבות·שער ראשון - שער ייחוד א׳

1The author says:

2The definition of the wholehearted acceptance of the unity of G-d is that the heart and the tongue are equal in acknowledging the unity of G-d, after understanding, in the way of logical proofs, the certainty of His existence and the truth of His unity. For acknowledgement of the unity of G-d among men differs according to their level of intelligence and understanding.

3Among them: One who declares the unity (of G-d) with only his tongue, namely, that he hears people say something and he is drawn after them without understanding the meaning of what he is saying.

4Among them: One who declares the unity of G-d with his heart and tongue, who understands the matter of what he is saying through the Tradition that he received from his ancestors, but he does not understand the clarification of what he received of this matter, and the truth of what he believes in this matter.

5Among them: One who declares His unity after understanding through logical proofs the truth of the matter, but he will conceive G-d's Unity like other unities to be found, and he will come to form a material conception of the Creator and represent Him with a form and likeness because he does not understand the true nature of His Unity and the matter of His existence.

6Among them: One who declares G-d's unity with his heart and with his tongue after understanding the concept of true unity versus relative unity, and he can bring proofs to demonstrate G-d's existence and true Unity - this class of men is the complete (unblemished) group regarding the matter of unity of G-d.

7Therefore, I defined the wholehearted acknowledgement of the unity (of G-d) - that it is the equalizing of the tongue and the heart (mind)) in the unity of the Creator, after one knows how to bring proofs on it and understands the ways of His true Unity through rational investigation.