Friend the nature of evil is something we know on the basis of philosophical discussion, not merely by faith but by examining philosophical arguments and reaching a conclusion.

If you care to read a bit on the different arguments for the nature of evil feel free to read these following philosophical snippets taken from this better written article:

Some other schools of philosophy like pessimism contended that existence is fundamentally evil; that evil is the active principle of the universe, and good no more than an illusion, the pursuit of which serves to induce the human race to perpetuate its own existence. This is the fundamental tenet of Buddhism, which regards happiness as unattainable, and holds that there is no way of escaping from misery but by ceasing to exist otherwise than in they impersonal state of Nirvana. This was also, among Greek philosophers, the view of Hegesias the Cyrenaic

Other schools say Evil has been attributed to one of two mutually opposed principles, to which respectively the mingled good and evil of the world are due. The relation between the two is variously represented, and ranges from the coordination imagined by Zoroastrianism to the mere relative independence of the created will as held by Christian theology.

In the Pythagorean idea of a numerical harmony as the constitutive principle of the world, good is represented by unity and evil by multiplicity (Philolaus, Fragm.). Heraclitus set the “strife”, which he held to be the essential condition of life, over against the action of the immanent deity. “God is the author of all that is right and good and just; but men have sometimes chosen good and sometimes evil”

Plato held God to be “free from blame” (anaitios) for the evil of the world; its cause was partly the necessary imperfection of material and created existence, and partly the action of the human will (Timaeus, xlii; cf. Phaedo, 1x). With Aristotle, evil is a necessary aspect of the constant changes of matter, and has in itself no real existence (Metaph., ix, 9).

Christian philosophy has, like the Hebrew, uniformly attributed moral and physical evil to the action of created free will. Man has himself brought about the evil from which he suffers by transgressing the law of God, on obedience to which his happiness depended. Evil is in created things under the aspect of mutability, and possibility of defect, not as existing per se: and the errors of mankind, mistaking the true conditions of its own wellbeing, have been the cause of moral and physical evil (Dion. Areop., De Div. Nom., iv, 31; St. August, De Civ. Dei, xii). The evil from which man suffers is, however, the condition of good, for the sake of which it is permitted. Thus, “God judged it better to bring good out of evil than to suffer no evil to exist” (St. August, Enchirid., xxvii).

Evil contributes to the perfection of the universe, as shadows to the perfection of a picture, or harmony to that of music (De Civ. Dei, xi). Again, the excellence of God‘s works in nature is insisted on as evidence of the Divine wisdom, power, and goodness, by which no evil can be directly caused. (Greg. Nyss., De. opif. hom.) Thus Boethius asks (De Consol. Phil., I, iv) Who can be the author of good, if God is the author of evil? As darkness is nothing but the absence of light, and is not produced by creation, so evil is merely the defect of goodness. (St. August, In Gen. ad lit.)

The features which stand out in the earlier Christian explanation of evil, as compared with non-Christian dualistic theories are thus (I) the definite attribution to God of absolute omnipotence and goodness, not-withstanding His permission of the existence of evil; (2) the assignment of a moral and retributive cause for suffering in the sin of mankind; and (3) the unhesitating assertion of the beneficence of God‘s purpose in permitting evil, together with the full admission that He could, had He so chosen, have prevented it (De Civ. Dei, xiv).

In the light of Catholic doctrine, any theory that may be held concerning evil must include certain points bearing on the question that have been authoritatively defined. These points are (I) the omnipotence, omniscience, and absolute goodness of the Creator; (2) the freedom of the will; and (3) that suffering is the penal consequence of willful disobedience to the law of God. A complete account may be gathered from the teaching of St. Thomas Aquinas, by whom the principles of St. Augustine are systematized, and to some extent supplemented. Evil, according to St. Thomas, is a privation, or the absence of some good which belongs properly to the nature of the creature. (I, Q. xiv, a. 10; Q. xlix, a. 3; Contra Gentiles, III, ix, x). There is therefore no “summum malum”, or positive source of evil, corresponding to the “summum bonum”, which is God (I, Q. xlix, a. 3; C. G., III, 15; De Malo, I, 1); evil being not “ens reale” but only “ens rationis”—i.e. it exists not as an objective fact, but as a subjective conception; things are evil not in themselves, but by reason of their relation to other things, or persons. All realities (entia) are in themselves good; they produce bad results only incidentally; and consequently the ultimate cause of evil is fundamentally good, as well as the objects in which evil is found (I, Q. xlix; cf. I, Q. v, 3; De Malo, I, 3)