[13] While Plato never directly stated the doctrine, it was developed, based on his remarks on evil, by the Neoplatonist philosopher Plotinus,[14] chiefly in the eighth tractate of his First Ennead.
Within this non-being are comprised all sense-objects, and all their passive modifications; or, evil may be something still more inferior, like their accident or principle, or one of the things that contribute to its constitution.
To gain some conception of evil it may be represented by the contrast between measure and incommensurability; between indetermination and its goal; between lack of form and the creating principle of form; between lack and self-sufficiency; as the perpetual unlimited and changeableness; as passivity, insatiableness, and absolute poverty.
[21]Augustine also mentioned the doctrine in passing in his City of God, where he wrote that "evil has no positive nature; but the loss of good has received the name 'evil.
[7] The theologian Pseudo-Dionysius the Areopagite also states that all being is good, in Chapter 4 of his work The Divine Names.
"[23][11] Thomas Aquinas concluded, in article 1 of question 5 of the First Part of his Summa Theologiae, that "goodness and being are really the same, and differ only in idea".
The philosopher Baruch Spinoza also agreed with the doctrine, when he said: "By reality and perfection I mean the same thing" (Ethics, part II, definition VI).
[6][24] He clarified this definition in the preface to part IV of the same work:Perfection and imperfection, then, are in reality merely modes of thinking, or notions which we form from a comparison among one another of individuals of the same species; hence I said above (II.
Thus, in so far as we refer the individuals in nature to this category, and comparing them one with another, find that some possess more of being or reality than others, we, to this extent, say that some are more perfect than others.
For, inasmuch as we desire to form an idea of man as a type of human nature which we may hold in view, it will be useful for us to retain the terms in question, in the sense I have indicated.
A typical example is Bertrand Russell, who criticized the doctrine in his essay The Elements of Ethics: [...] the belief that, as a matter of fact, nothing that exists is evil, is one which no one would advocate except a metaphysician defending a theory.
Pain and hatred and envy and cruelty are surely things that exist, and are not merely the absence of their opposites; but the theory should hold that they are indistinguishable from the blank unconsciousness of an oyster.
Indeed, it would seem that this whole theory has been advanced solely because of the unconscious bias in favour of optimism, and that its opposite is logically just as tenable.
Consequently it is a condition of goodness, that, supposing an evil to be present, sorrow or pain should ensue.
Hacker, in his book The Moral Powers, repeated the counter-example of cruelty, also mentioned by Russell: "The idea that evil is privative, that is, it consists in the absence of good, stripped of its theological trappings, is unconvincing.
"[32] Immanuel Kant believed that, while the doctrine is true of concepts of the understanding, it is nevertheless false about the world as it appears to the senses.
For real opposition, in which A − B is = 0, exists everywhere, an opposition, that is, in which one reality united with another in the same subject annihilates the effects of the other—a fact which is constantly brought before our eyes by the different antagonistic actions and operations in nature, which, nevertheless, as depending on real forces, must be called realitates phaenomena.
According to this principle, for example, all evils are but consequences of the limited nature of created beings, that is, negations, because these are the only opposite of reality.
In like manner, the upholders of this system deem it not only possible, but natural also, to connect and unite all reality in one being, because they acknowledge no other sort of opposition than that of contradiction (by which the conception itself of a thing is annihilated), and find themselves unable to conceive an opposition of reciprocal destruction, so to speak, in which one real cause destroys the effect of another, and the conditions of whose representation we meet with only in sensibility.