the heart of the sons of men is full of evil, and madness is in their heart while they live, and after that they go to the dead - Eccl. 9:3
If this is literally saying that all human hearts are filled with evil, then it is equally true that all of us are suffering from madness until the day we die. But that is not what the text really means. Even if it were literal, it still doesn’t say humans inherited sin from Adam.
Yes it does mean what it says. It is perfectly clear. All sin is illogical because it is ultimately harmful, whether acknowledged or not. Sin is madness. And of course it is inherited because it is describing the "sons of men" as a group. If not from ancestors, from where then does it come?
Consider these comments:
Wickedness is spoken of in other places in the book of Psalms, as a thing that belongs to men, as of the human race, as sons of men. Thus, in Psa. 4:2, “O ye sons of men, how long will ye turn my glory into shame? How long will ye love vanity?” etc. Psa. 57:4, “I lie among them that are set on fire, even the sons of men, whose teeth are spears and arrows, and their tongue a sharp sword.” Psa. 58:1, 2, “Do ye indeed speak righteousness, O congregation? Do ye judge uprightly, O ye sons of men? Yea, in heart ye work wickedness; ye weight out the violence of your hands in the earth.” Our author mentioning these places, says (p. 105. note), “There was a strong party in Israel disaffected to David’s person and government, and sometimes he chooseth to denote them by the sons or children of men.” But it would have been worth his while to have inquired, Why the psalmist should choose to denote the worst men in Israel by this name? Why he should choose thus to disgrace mankind, as if the compellation of sons of men most properly belonged to such as were of the vilest character, and as if all the sons of men, even every one of them, were of such a character, and none of them did good; no, not one? Is it not strange, that the righteous should not be thought worthy to be called sons of men, and ranked with that noble race of beings, who are born into the world wholly right and innocent? It is a good, easy, and natural reason, why he chooseth to call the wicked, sons of men, as a proper name for them, That by being of the sons of men, or of the corrupt, ruined race of mankind, they come by their depravity. And the psalmist himself leads us to this very reason, Psa. 58, “Do ye judge uprightly, O ye sons of men? yea, in heart ye work wickedness ye weigh out the violence of your hands. The wicked are estranged from the womb,” etc. Of which I shall speak more by and by.
Agreeable to these places is Pro. 21:8, “The way of man is froward and strange; but as for the pure, his work is right.” He that is perverse in his walk, is here called by the name of man, as distinguished from the pure: which I think is absolutely unaccountable, if all mankind by nature are pure, and perfectly innocent, and all such as are froward and strange in their ways, therein depart from the native purity of all mankind. The words naturally lead us to suppose the contrary; that depravity and perverseness properly belong to mankind as they are naturally, and that a being made pure, is by an after-work, by which some are delivered from native pollution, and distinguished from mankind in general.
To these things agree Jer. 17:5, 9. In verse 5, it is said, “Cursed is he that trusteth in man.” And in verse 9, this reason is given, “The heart is deceitful above all things, and desperately wicked; who can know it?” What heart is this so wicked and deceitful? Why, evidently the heart of him, who, it was said before, we must not trust; and that is MAN. It alters not the case as to the present argument, whether the deceitfulness of the heart here spoken of, be its deceitfulness to the man himself, or to others. So - Ecc. 9:3, “Madness is in the heart of the sons of men, while they live.”...
How strange is it, that we should have such descriptions, all over the Bible, of MAN, and the SONS OF MEN! Why should man be so continually spoken of as evil, carnal, perverse, deceitful, and desperately wicked, if all men are by nature as perfectly innocent, and free from any propensity to evil, as Adam was the first moment of his creation, all made right, as our author would have us understand Ecc. 7:29? Why, on the contrary, is it not said, at least as often, and with equal reason, that the heart of man is right and pure; that the way of man is innocent and holy; and that he who savors true virtue and wisdom, savors the things that be of men? Yea, and why might it not as well have been said, the Lord looked down from heaven on the sons of men, to see if there were any that did understand, and did seek after God; and they were all right, altogether pure, there was none inclined to do wickedness, no, not one?