This post takes the two doctrines, Christianity and Islam, together, in that order, because the diagnosis determines the cure. What a religion says is wrong with human beings decides in advance what it can offer as a remedy. Islam teaches that every person is born in a state of fitrah — an innate purity oriented toward Allah — and therefore needs guidance, law, and warning; salvation follows accordingly as a weighing of deeds against Allah's mercy. Christianity teaches that human nature, though made in God's image, is corrupted at the root by Adam's sin and therefore needs a new birth rather than instruction alone; salvation follows accordingly as a finished substitutionary atonement received by grace through faith.

Human Nature — Fitrah vs. Inherited Corruption

What Islam Teaches: Fitrah — Born Innocent, Individually Accountable

Islamic anthropology holds that every human being is born in a state of fitrah — an innate, pure disposition oriented toward recognizing and submitting to Allah, uncorrupted by any inherited guilt from Adam's sin:

"So be steadfast in faith in all uprightness ˹O Prophet˺—the natural Way of Allah which He has instilled in ˹all˺ people. Let there be no change in this creation of Allah. That is the Straight Way, but most people do not know." — Qur'an 30:30

A well-known Hadith reinforces this:

"No child is born except on Al-Fitra (Islam) and then his parents make him Jewish, Christian or Magian, as an animal produces a perfect young animal: do you see any part of its body amputated?" — Sahih al-Bukhari 4775

Consistent with this, the Qur'an teaches individual moral accountability rather than inherited guilt:

"Whoever chooses to be guided, it is only for their own good. And whoever chooses to stray, it is only to their own loss. No soul burdened with sin will bear the burden of another. And We would never punish ˹a people˺ until We have sent a messenger ˹to warn them˺." — Qur'an 17:15; cf. 35:18; 53:38

"And by the soul and ˹the One˺ Who fashioned it, then with ˹the knowledge of˺ right and wrong inspired it! Successful indeed is the one who purifies their soul, and doomed is the one who corrupts it!" — Qur'an 91:7–10

On this reading, every person is born with the innate capacity to discern right from wrong and a built-in orientation toward Allah; sin, when it happens, is a personal act of straying from that created nature, not the outworking of an inherited corruption transmitted from Adam. Some contemporary Muslim writers describe this framework as "Original Forgiveness" rather than "Original Sin," pointing to the Qur'an's account that Adam repented and Allah accepted his repentance (Qur'an 2:37):

"Then Adam was inspired with words ˹of prayer˺ by his Lord, so He accepted his repentance. Surely He is the Accepter of Repentance, Most Merciful." — Qur'an 2:37

It should be noted, in fairness to the range of Islamic scholarship on this question, that the Qur'an's account of the Fall does still describe Adam being expelled from the Garden together with his offspring in language some classical commentators (including Ibn Kathir) read as extending consequence, though not necessarily inherited guilt, to his descendants (Qur'an 2:36; 7:24, where the second-person plural forms are addressed to Adam, Eve, and — in the reading of many exegetes — their offspring). Whatever weight is given to that detail, the settled and majority position of Sunni orthodoxy is that no soul bears the guilt of another's sin, and that human nature itself remains fundamentally pure at the point of birth.

What Christianity Teaches: Made in God's Image, Corrupted by Adam's Sin

Scripture's starting point on human nature is high: every person is made in God's own image. "God created man in His own image, in the image of God He created him; male and female He created them" (Genesis 1:27). This is not a doctrine Christianity abandons or qualifies away — human dignity and worth in Christian theology rest on this creation in the imago Dei, a category Scripture never revokes even after the Fall (cf. Genesis 9:6, where murder remains a uniquely grave sin precisely because the victim still bears God's image, generations after Eden).

Yet the Bible also teaches that what entered the world through Adam did not remain Adam's alone. Paul's account of how it passed to everyone after him is precise, and worth reading slowly:

"Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned." — Romans 5:12

Two things enter through one man — sin, and death through sin — and the consequence Paul states explicitly is that death "spread to all men." The verb is Greek διῆλθεν (diēlthen, Strong's G1330), "passed through" or "spread throughout," used of something traveling across a whole territory until no part of it is left untouched (BDAG, 3rd ed., s.v. διέρχομαι). He then grounds that universal death in a universal fact: "because all sinned" — Greek ἐφ᾽ ᾧ πάντες ἥμαρτον (eph' hō pantes hēmarton). The connective ἐφ᾽ ᾧ is causal, "because" (BDAG, 3rd ed., s.v. ἐπί). Jerome's Latin rendered it in quo, "in whom," and Augustine built on that rendering the claim that all humanity sinned inside Adam; the Greek relative does not carry that sense, and the NASB95's "because" reflects the reading the grammar actually supports. Taken by itself, then, verse 12 establishes universal death traced to one man and universal sinning — it does not yet state the mechanism.

The mechanism arrives a few verses later, and so does the end of Paul's sentence. Verse 12 breaks off mid-comparison — "just as..." never receives its answering "so also" — and the thought is not completed until Romans 5:18–19: one man's righteous act becomes the basis on which many are counted righteous, exactly as one man's disobedience became the basis on which "the many were made sinners" (Romans 5:19). The verb "were made" — Greek κατεστάθησαν (katestathēsan, from καθίστημι, Strong's G2525) — means "were constituted" or "were appointed," an official and binding designation rather than an environmental influence each person could in principle sidestep (BDAG, 3rd ed., s.v. καθίστημι). Adam's descendants are not merely imitators of his choice; they are constituted sinners by it.

And Scripture states plainly that what results is a matter of nature, not merely of record: "we too all formerly lived in the lusts of our flesh... and were by nature children of wrath, even as the rest" (Ephesians 2:3). The word is "nature" — Greek φύσει (physei, from φύσις, Strong's G5449) — the condition a thing possesses by birth and constitution rather than by later habit (BDAG, 3rd ed., s.v. φύσις). The same testimony runs the length of the canon: "the intent of man's heart is evil from his youth" (Genesis 8:21); "Behold, I was brought forth in iniquity, and in sin my mother conceived me" (Psalm 51:5); "The heart is more deceitful than all else and is desperately sick" (Jeremiah 17:9); "That which is born of the flesh is flesh" (John 3:6). Paul describes the condition from the inside — "nothing good dwells in me, that is, in my flesh" (Romans 7:18) — and names its consequence: the mind set on the flesh "does not subject itself to the law of God, for it is not even able to do so" (Romans 8:7).

That final clause is where the two anthropologies part company most sharply. The fitrah framework holds that human nature retains the capacity to respond rightly once properly instructed; Paul's claim is that the capacity itself is what has been damaged. The solidarity that results is stated in a single line:

"For as in Adam all die, so also in Christ all will be made alive." — 1 Corinthians 15:22

At the same time, Scripture agrees with the Qur'an's insistence that individuals are judged for their own actions and not made guilty merely by another's sin considered in isolation from their own participation in it: "The person who sins will die. A son will not bear the punishment for the father's iniquity, nor will a father bear the punishment for the son's iniquity" (Ezekiel 18:20). Christian theology reads Romans 5 and Ezekiel 18 as complementary rather than contradictory: humanity inherits from Adam a corrupted nature and its consequence (death, Romans 5:12), while each individual is still held responsible before God for what he does with that nature — a distinction between inherited condition and personal culpability that most classical Christian traditions (again, apart from a specifically Reformed/Calvinist formulation of inherited guilt as personal culpability from birth, which this study does not adopt as the interpretive lens) have historically maintained.

The practical difference this makes for the rest of each system is significant. If human nature is fundamentally pure at birth and needs only guidance (the fitrah framework), then the appropriate remedy for sin is instruction, warning, and a system of law and reward — which is exactly the shape Islamic soteriology takes, as the next section shows. If human nature is corrupted at the root and in bondage to sin from within (the biblical framework), then instruction and law, however good, cannot supply what is actually needed — "if a law had been given which was able to impart life, then righteousness would indeed have been based on law" (Galatians 3:21) — and what is needed instead is a new birth, a change of nature accomplished by God Himself: "you must be born again" (John 3:7); "if anyone is in Christ, he is a new creature; the old things passed away; behold, new things have come" (2 Corinthians 5:17).

Salvation & Atonement — Deeds Weighed by Mercy vs. Substitution Received by Grace

What Islam Teaches: Salvation Through the Balance of Deeds and Allah's Mercy

Islamic soteriology centers on the Day of Judgment, when Allah will weigh each person's deeds:

"We set up the scales of justice for the Day of Judgment, so no soul will be wronged in the least. And ˹even˺ if a deed is the weight of a mustard seed, We will bring it forth. And sufficient are We as a ˹vigilant˺ Reckoner." — Qur'an 21:47

"So as for those whose scale is heavy ˹with good deeds˺, they will be in a life of bliss. And as for those whose scale is light, their home will be the abyss." — Qur'an 101:6–9

Forgiveness in this framework depends on a combination of sincere repentance, right belief (specifically, the Shahada — "there is no god but Allah, and Muhammad is His messenger" — and rejection of shirk), and the outweighing of bad deeds by good ones (Qur'an 3:135; 7:8–9; 66:8). The Five Pillars of Islam — the Shahada (creed), Salat (five daily prayers), Sawm (fasting during Ramadan), Zakat (almsgiving), and Hajj (pilgrimage to Mecca) — are the framework of obligatory worship and practice by which a Muslim maintains standing within the faith; a Muslim who fulfills them, remains within Islam, and sincerely repents is taught to hope for Jannah (Paradise), but the Qur'an nowhere promises any individual believer certainty of that outcome in advance. A well-known hadith captures this candidly from Muhammad's own reported words about himself and those closest to him. Um Al-'Ala had just declared of a dead companion, "I bear witness that Allah has honored you," and was corrected:

"The Prophet said, 'How do you know that Allah has honored him?' I replied, 'I do not know...' He said, 'As to him, by Allah, death has overtaken him, and I hope the best for him. By Allah, though I am the Apostle of Allah, yet I do not know what Allah will do to me.'" — Sahih al-Bukhari 3929

The Qur'an puts the same admission in Muhammad's mouth directly:

"Say, 'I am not the first messenger ever sent, nor do I know what will happen to me or you. I only follow what is revealed to me. And I am only sent with a clear warning.'" — Qur'an 46:9

Salvation in Islam, honestly stated in the terms of its own primary sources, is a matter of hope grounded in Allah's mercy and one's own weighed record, not a settled assurance grounded in a finished transaction.

What Christianity Teaches: Salvation by Grace Through Faith, Grounded in a Finished Atonement

Scripture agrees with the Qur'an that human beings are sinful and that judgment is real and coming (compare Romans 2:5–6: God "will render to each person according to his deeds"). The decisive difference is how sin is dealt with: not primarily by a favorable balance of deeds outweighing sins, but by a substitutionary death that satisfies the demands of justice on behalf of the sinner, received as a gift rather than earned as a wage.

"For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast." — Ephesians 2:8–9

The word "grace" — Greek χάρις (charis, Strong's G5485; BDAG, 3rd ed., s.v. χάρις) — denotes unearned favor — a gift given not because of the recipient's merit but from the giver's own generosity. Paul's point is structural, not incidental: salvation is "not of yourselves," "not as a result of works," specifically "so that no one may boast" — a direct exclusion of any framework in which a person's good deeds, weighed against bad, become the basis of acceptance before God.

The mechanism by which this grace operates is substitutionary atonement — Christ's death standing in the place of sinners, satisfying the just penalty for sin so that forgiveness can be extended without compromising God's justice:

"He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him." — 2 Corinthians 5:21

"But He was pierced through for our transgressions, He was crushed for our iniquities; The chastening for our well-being fell upon Him, And by His scourging we are healed." — Isaiah 53:5

Isaiah 53 — written some seven centuries before Christ — describes a suffering servant figure who bears the guilt of others substitutionally: "the LORD has caused the iniquity of us all to fall on Him" (Isaiah 53:6). John Oswalt, in the NICOT volume on Isaiah, treats this servant figure as pointing beyond any purely national or collective referent to an individual whose vicarious suffering accomplishes what the people's own suffering could not ^[1]. The New Testament explicitly identifies Jesus as the fulfillment of this figure: the Ethiopian eunuch is reading Isaiah 53 when Philip "preached Jesus to him," beginning with that very passage (Acts 8:32–35).

This is why the crucifixion — denied by the Qur'an — is not a peripheral historical dispute but the theological hinge of the entire soteriological difference between the two faiths. If Christ did not die, there is no atoning sacrifice; the Christian doctrine of salvation by grace through a finished substitutionary work collapses without it, and salvation would have to revert to some version of the deeds-based framework Islam already teaches. Conversely, if Christ did die and rise as the New Testament and the wider historical record indicate, then the Qur'an's alternative account of the crucifixion is not simply a different detail but a claim that removes the very event Christianity identifies as its Savior's saving work.

Assurance is the other point of sharp divergence. Where Islamic sources candidly present the believer's ultimate fate as unknown even to Muhammad himself, the New Testament repeatedly grounds the believer's confidence not in the sufficiency of his own record but in the sufficiency of Christ's finished work: "These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life" (1 John 5:13); "there is therefore now no condemnation for those who are in Christ Jesus" (Romans 8:1). This assurance is not presented as presumption but as the appropriate response to a debt Scripture says has already been paid in full: "having canceled out the certificate of debt... having nailed it to the cross" (Colossians 2:14).