1) Man's Heart is Evil
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Mark 7:20-23
20 And He said, "That which comes out of a man, that defiles a man.
21 For from within, out of the heart of men, come forth evil thoughts, adulteries, fornications, murders,
22 thefts, covetousness, wickedness, deceit, lewdness, an evil eye, blasphemy, arrogance, foolishness.
23 All these evil things come from within and defile a man."
Question: Evil wants and wills and thoughts and deeds can come forth out from the hearts of men. But cannot also fidelity, truth, humility, and a helping hand come forth as well? Do we not see such all the time, for example, America's privately given aid to disaster victims? What makes Mark 7:21-23 exclusive -- to wit, how does the text read, "for from within, out of the heart of men, only come forth evil..."?
2) Man's Heart is Sick
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Jeremiah 17:9 (LXX): The heart is deep beyond all things, and {1} it is the man, and who can know him?
It is only in the Masoretic Text -- the textual tradition of the very Jews who did, at the end of the day, reject their own Messiah -- that the wording reads "the heart is deceitful...".
However, the word rendered "Deep" in the LXX for Jeremiah 17:9 means "Abyss" and is linked to the concept of "Sheol / Hell". So even the LXX does seem to say, in Jeremiah's name, that the "hearts of men are Hellish Abysses". And according to the LXX translator Brenton, Jeremiah 17:9 hearkens back to Bywords (Proverbs) 27:19. Interestingly, the link to Bywords 27:19 makes no sense in the LXX, whose reading is only vaguely similar to the Masoretic -- which in this case does seem a better reference indeed:
Bywords 27:19-20 (Darby)
19 As [in] water face [answereth] to face, so the heart of man to man.
20 Sheol and destruction are insatiable; so the eyes of man are never satisfied.
Thus, the reference Brenton highlights seems to be, from Jeremiah 17:9 to Bywords 27:19-20, saying that "the hearts of men are insatiable abysses", or even, "the hearts of men are hellish insatiable abysses".
But, for sake of scholarly fullness, the LXX has for Bywords 27:19, "As faces are not like other faces, so neither are the thoughts of men." (The LXX reads the same for line (verse) 20.) So, given that both the LXX and Masoretic texts both came from an even deeper and older layer of tradition, the original sense would seem to have been that, while certainly some men's hearts are indeed "hellish insatiable abysses", that also men are not all the same, and that by holding up a mirror, you can deem them to be either good or bad.
So again, while their is partial support for the Calvinist doctrine, I do not see that there is any fundamental Scriptural assertion that men are exclusively depraved -- only that some are.
3) Man is a Thrall of Sin
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Romans 6 (EMTV)
16 Do you not know that to whom you present yourselves as obedient slaves, you are slaves to whom you obey, whether of sin resulting in death, or of obedience resulting in righteousness?
17 But thanks be to God, that though you used to be slaves of sin, yet you obeyed from your heart that form of doctrine to which you were delivered.
18 And having been freed from sin, you became enslaved to righteousness.
19 I speak in human terms on account of the weakness of your flesh. For just as you presented your members as slaves to uncleanness, and to lawlessness resulting in more lawlessness, so now present your members as slaves to righteousness resulting in sanctification.
20 For when you were slaves of sin, you were free in regard to righteousness.
21 So what fruit did you have then of which things you are now ashamed? For the end of those things is death.
22 But now having been freed from sin, and having become enslaved to God, you have your fruit resulting in sanctification, and the outcome, eternal life.
23 For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.
Earlier in the Chapter (Romans 6:4), Saul Paulus links Baptism to the "Death & Quickening" ("Passion and Resurrection") of the Messiah -- to wit, Baptism is a symbolic re-enactment of the Messiah's trial on the cross, his burial, and his re-emergence.
Now hear this! Now hear this! IF you accept Believer's Dunking (Baptism) -- that is, a True and Lawful Dunking is only and solely for those who Truly and Freely Choose to Believe in the Messiah -- then you are PRE-SUPPOSING Free Will.
And Saul Paulus goes on, up through the quoted block above, to link that Dunking -- and Baptists read, "Believer's Dunking", yes? -- to a "death of the old to sin" and a "new life to God" that breaks our shackles to our (past) sins and frees us to our new life (see also Gal 2:4, 5:1, 5:13).
Therefore, the doctrine of "Believer's Dunking", which is built upon "Free Will", bids us acknowledge that the FREE CHOICE to (truly) Believe in the Messiahship of Yeshua BREAKS our bonds to sin! That is, OUR FREE WILL alone, all by itself, is ENOUGH to BREAK OUR CHAINS and FREE US from THRALLDOM to sin!
Therefore, when Calvinists cite Romans 6:20 as proof that "man is thralled to sin", they are clearly refering to the pre-Baptismal (afore-dunked) state! But 2 lines later we read, "BUT now having been freed..." by the Believer's Dunking which embodies his death & quickening (death & resurrection).
Therefore, if you want to claim "predestination", for example, you must now also claim that some people are PRE-ORDAINED to undergo DUNKING / BAPTISM! Some folks are just COMPELLED to do it, others aren't.
In a sense, Calvinists SIDE-STEP this argument by, I think, accepting INFANT BAPTISM which does completely DOWN PLAY the CRUCIAL IMPORTANCE of BAPTISM / DUNKING.
This is getting long so I'll stop here for now.