Scripture is quite clear that all that pertains to Salvation is a spiritual matter, and man by nature has no spiritual life and perception. The natural man cannot know the things of the Spirit of God, because they must be Spiritually discerned, that goes for the Gospel a Spiritual message/revelation. 1 Cor 2:13-14
12 Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God.
13 Which things also we speak, not in the words which man's wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.
14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.
This is simply showing the carnal man, the man who judges solely by earthly wisdom cannot receive revelation knowledge from the spirit regarding things which are hid in the mind of God. It does not say man cannot understand the revealed gospel
John 12:40 (KJV 1900) — 40 He hath blinded their eyes, and hardened their heart; that they should not see with their eyes, nor understand with their heart, and be converted, and I should heal them.
God blinded men to prevent their belief. Why would God blind someone who had no ability to see?
Why prevent from believing those who had no capacity for belief
Luke notes had men not grown hardened they could have believed
Acts 28:27 (KJV 1900) — 27 For the heart of this people is waxed gross, and their ears are dull of hearing, and their eyes have they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them.
Jesus clearly states he hides truth for some as otherwise they would repent and be forgiven
Mark 4:10–12 (ESV) — 10 And when he was alone, those around him with the twelve asked him about the parables.
11 And he said to them, “To you has been given the secret of the kingdom of God, but for those outside everything is in parables,
12 so that “ ‘they may indeed see but not perceive, and may indeed hear but not understand, lest they should turn and be forgiven.’ ”
unregenerate men are shown to receive the word with joy and believe
Luke 8:13 (KJV 1900) — 13 They on the rock are they, which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away.
The adversary steals the word away so men will not believe
Luke 8:11–12 (KJV 1900) — 11 Now the parable is this: The seed is the word of God. 12 Those by the way side are they that hear; then cometh the devil, and taketh away the word out of their hearts, lest they should believe and be saved.
What need is there to steal away a word which cannot be believed?
John 1:6–7 (KJV 1900) — 6 There was a man sent from God, whose name was John. 7 The same came for a witness, to bear witness of the Light, that all men through him might believe.
John the apostle believes the testimony of John the Baptist is sufficient for faith.
John 5:45–47 (KJV 1900) — 45 Do not think that I will accuse you to the Father: there is one that accuseth you, even Moses, in whom ye trust. 46 For had ye believed Moses, ye would have believed me: for he wrote of me. 47 But if ye believe not his writings, how shall ye believe my words?
John 4:39 (KJV 1900) — 39 And many of the Samaritans of that city believed on him for the saying of the woman, which testified, He told me all that ever I did.
How much exegesis is needed to see men believed based upon the woman's testimony
John 17:20 (KJV 1900) — 20 Neither pray I for these alone, but for them also which shall believe on me through their word;
men will be able to believe based on the apostle's testimony
John 20:31 (KJV 1900) — 31 But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.
The reading of scripture is sufficient for belief
2 Timothy 3:15 (NIV) — 15 and how from infancy you have known the Holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus.
Ephesians 3:4–11 (NIV) — 4 In reading this, then, you will be able to understand my insight into the mystery of Christ, 5 which was not made known to people in other generations as it has now been revealed by the Spirit to God’s holy apostles and prophets. 6 This mystery is that through the gospel the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus. 7 I became a servant of this gospel by the gift of God’s grace given me through the working of his power. 8 Although I am less than the least of all the Lord’s people, this grace was given me: to preach to the Gentiles the boundless riches of Christ, 9 and to make plain to everyone the administration of this mystery, which for ages past was kept hidden in God, who created all things. 10 His intent was that now, through the church, the manifold wisdom of God should be made known to the rulers and authorities in the heavenly realms, 11 according to his eternal purpose that he accomplished in Christ Jesus our Lord.
As is the preaching of it.
Romans 10:10–17 (KJV 1900) — 10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. 11 For the scripture saith, Whosoever believeth on him shall not be ashamed. 12 For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him. 13 For whosoever shall call upon the name of the Lord shall be saved. 14 How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher? 15 And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things! 16 But they have not all obeyed the gospel. For Esaias saith, Lord, who hath believed our report? 17 So then faith cometh by hearing, and hearing by the word of God.
Acts 28:23–24 (KJV 1900) — 23 And when they had appointed him a day, there came many to him into his lodging; to whom he expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening.
24 And some believed the things which were spoken, and some believed not.
That is the problem with Calvinism. It takes a verse here and a verse there and divorces it from the overall biblical context, disregarding the fact that its conclusions are contrary to many verses of scripture.