Unity of Attributes in the view of the Theologians and Philosophers

Source: The Learning of the Glorious Qur’an, by Ayatullah Misbah Yazdi page 77.

At-Tawhid in attributes means that the attributes which we ascribe to Allah are nothing but His very Essence they are not things other than Himself added to Him, such as the case with us, the human beings and our attributes. If a black object wanted to be white, a colour is to be added to it to make it white. Similar are the moral characteristics. A sad person may become happy by adding to him a mood of happiness. To the one who dislikes work we may add the required attribute to make one like it and want it.
So, there is a being who lacks the will, then the will can be added to him - an addition which suits the soul and abstract things, then it finds what it has not had before. Thus, it becomes clear that the soul itself is something and the will is something else. The soul was there, but the will was not there, then later there was the will added to the soul and the soul has acquired the will. So, the wanted attribute can be ascribed to the soul only when something other than the soul is added to it.
All the attributes which we recognize in the substances and non-substances, such as the psychological attributes, are all of this type, that is, the attribute is something other than the essence. Is it the same with Allah, the Most High, too? Is this Essence something other than His knowledge? If so, does it mean that, if we disregard His knowledge, the Essence itself will lack knowledge? Is Allah's power something other than His Essence? Does it mean that His Essence, in itself, is lacking power which is added to it afterwards, and only then we say: Allah is powerful? Is it so? It is said that the Ash'aris (a Sunni sect) say that Allah's Attributes are other than His Essence, as Allah Himself is a truth that has eight Attributes, each one of them is self-existent, but they are not His very Essence, though they are old. That is why the Ash'aris were called "The Old Eights", one is Allah's Essence, and the others are the Attributes of His Essence.
On the opposite side of this opinion (which is untrue) stands the belief of the other intellectual Muslims, both the philosophers and the theologians, who say that Allah's Attributes are His very Essence, which is simple. Our minds derive different concepts from this Essence. The origin of all these concepts is the Essence itself, and it is the mind that derives these concepts through diverse view points concerning Allah, the Exalted. Such concepts have been formerly derived from another source, but they are concepts that speak of perfection.

Realizing that Allah is devoid of imperfection, the intellect says that He also has that perfection. But that perfection is nothing but His Essence. We first recognize the meaning of knowledge in ourselves. Is it possible that the one who has created this world is devoid of knowledge? It is impossible for the one who has no knowledge to create such a world so wisely. So, we say: "Allah is Knowing", or "Wise". These concepts are recognized first in ourselves, but we ascribe them to Allah, as we know that Allah possesses all perfections. So, the source from which these concepts are derived is the Sacred Divine Essence. Knowledge is not a separate thing annexed, or added, to Allah, or united with Him. It is the Simple Divine Essence that causes the mind to ascribe these concepts to it. The expression that the Divine Attributes are nothing but the very Essence -of Allah is called, in the terms of the philosophers and theologians, "at-Tawhid in Attributes" or the unity of Attributes. Maybe what has Imam `Ali (A.S.) said in "Nahjul-Balaghah" was a reference to this. He said: "The perfect admission of His Oneness is to deny Him attribute." Oneness can be perfect only when we deny Him the attributes which are not His very Essence; not to ascribe to Him the knowledge which is outside Him or is contrary to His Essence, otherwise at-Tawhid will be imperfect, and we will be accepting a kind of multiplicity: there is Allah, and there is His Knowledge, His Power, His Existence or else. Therefore, Unity of Attributes, as believed in by the philosophers and the theologians, means that Allah has no separate Attributes added to His Essence.