God created the Tree of Knowledge of Good and Evil and placed it in the Garden of Eden. So could there have been the knowledge of evil if evil itself had actually not been in existence created by God? We know from the Scriptures that everything in existence doesn't exist without God having created it. It seems likely Satan was created to be the servant of God for evil in the service of God's specific purposes in the outworking of history.
The Scriptures declare in Job 12:16:
With him is strength and wisdom: the deceived and the deceiver are his.
Does God not have to be the source of evil for the Bible to say that an evil spirit from God came on Saul in 1 Samuel 18:20?
Also, what is the meaning, what does one think, of 1 Kings 22:20-23 if the source of evil is to be found in an entity independent of God?
And the LORD said, Who shall persuade Ahab, that he may go up and fall at Ramothgilead? And one said on this manner, and another said on that manner. And there came forth a spirit, and stood before the LORD, and said, I will persuade him. And the LORD said unto him, Wherewith? And he said, I will go forth, and I will be a lying spirit in the mouth of all his prophets. And he said, Thou shalt persuade him, and prevail also: go forth, and do so. Now therefore, behold, the LORD hath put a lying spirit in the mouth of all these thy prophets, and the LORD hath spoken evil concerning thee.
And can there be any entity existing independently of the creative will of God?