The five solas of the Protestant Reformation remind us of the gospel truth that the Reformers recaptured: that salvation is by grace alone (sola gratia) through faith alone (sola fide) in Christ alone (solus Christus) according to Scripture alone (sola scriptura) for the glory of God alone (soli Deo gloria). The Reformers believed that this gospel had been lost to the Catholic Church and returned it front and centre in their churches.

Protestants sometimes draw a simplistic distinction between the Catholic gospel and the Protestant gospel. While Protestants teach salvation by grace, they say, Catholics teach salvation by works. While there is some truth to this distinction, the reality is far more complex than this formula suggests. Catholics have little problem affirming that salvation is by grace alone, but they object to the MEANS by which this grace is conferred: through faith alone. In Catholic thought, grace is conferred through faith AND works. At its root, this disagreement comes down to one basic truth: the doctrine of total depravity. The Reformers understood that humans are totally depraved—incapable of performing any good deed to merit God’s favour, or to add to the merit that God gives by his grace. Catholic doctrine objects that humans, even in their lost state, are indeed, by virtue of common grace, capable of meritorious works.

When it comes to a proper understanding of sin, which is the subject of Confession 3.5, it is imperative that we understand total depravity, for total depravity is really the root cause of actual sin.

The Confession states:

“Sin is rebellion against God and his law (Romans 1:21; Ephesians 2:1–3; 1 John 3:4). It expresses itself in acts of disobedience by doing what he prohibits and failing to do what he requires (Ephesians 2:1).”(Sola 5 Confession 3.5)

The Confession begins with a simple definition of sin: “Sin is rebellion against God and his law.” Perhaps the most direct definition in the Bible of sin comes from 1 John 3:4, which says simply, “Sin is lawlessness.” If we take this basic definition as a starting point, we might say that sin is any word, thought, deed, or motive that runs contrary to God’s law. We sin when we say, think, or do, or motivate anything that God forbids, or fail to say, think, do, or motivate anything that God commands. Sin is committed by commission and by omission.

The Confession cites Romans 1:21, which speaks of sin as failure to honour God as God or to give thanks to him. Honour and thanksgiving intrinsically belong to the Lord (Revelation 5:12–13; 7:12). To fail to give honour and thanks to him is to take from him what he rightly deserves. It is to give him less than what it is due. It is to rob him of what rightly belongs to him.

Ephesians 2:1–3, also cited in the Confession, speaks of us being “dead in the trespasses and sins in which [we] once walked.” It adds that we “were by nature children of wrath, like the rest of mankind.” There are three basic understandings of what it means that sin is part of our “nature.”

Pelagianism says that the only effect that Adam’s sin had on his descendants was to set a sinful example, which influences us to sin. Humans have the ability to stop sinning if they simply choose to.

Arminianism teaches that Adam’s sin has resulted in the rest of mankind inheriting a propensity to sin, commonly referred to as having a “sin nature.” This sin nature means that sin comes naturally to us. It also means that God’s grace is necessary for us to stop sinning. God has provided this grace universally to humankind, so that anyone can choose or refuse to resist sin and obey God. Even though we inherited a sin nature, we are not accountable in any way for Adam’s sin, only our own.

Calvinism teaches that Adam’s sin has resulted not only in our having a sin nature, but also in our incurring guilt before God for which we deserve punishment. We sinned in Adam, which means that our sin nature is so utterly wicked that we are entirely incapable of resisting sin and choosing righteousness apart from God’s specific, intervening grace in Jesus Christ.

When we take the full scriptural evidence into account—that we are conceived in sin (Psalm 51:5); that our heart is sinfully incurable (Jeremiah 17:9); that we sinned in, and therefore die in, Adam (Romans 5:12, 19), and that we are dead in our trespasses and sins (Ephesians 2:1–3)—the Calvinistic interpretation is most consistent with Scripture.

There is an interpretation of original sin that says we assume responsibility for original sin when we accept and act according to our sinful nature. According to this view, those who die in infancy or with some mental incapacitation, which renders them incapable of understanding and embracing their sin nature, will not be judged by God for their sin. They will, in effect, inherit eternal life.This is an area in which we do not have explicit biblical light. The texts that speak of final judgement certainly seem to highlight judgement based on direct, personal sin—sins committed “in the body” (2 Corinthians 5:10; cf. Revelation 20:11–12)—which may lend some credence to this theory. Regardless of one’s personal persuasion in this regard, we must affirm that God is a righteous judge who will always do what is right (Genesis 18:25; Isaiah 30:18) and leave those matters in his righteous hands.

The Confession recognises sin both in acts of commission and acts of omission: “It expresses itself in acts of disobedience by doing what he prohibits and failing to do what he requires.” It is probably accurate to say that many Christians think of sin more in terms of acts of commission (doing what God prohibits) than in terms of acts of omission (failing to do what he requires) (see James 4:7). That is dangerous, because it means that we can blind ourselves to sin and harden our conscience.

The biblical evidence for these two categories of sin is overwhelming. We see sins of commission, for example, in Genesis 2:16–17, where Adam and Eve deliberately disobeyed God by doing what he forbade. In the account of David and Bathsheba (2 Samuel 11), David likewise committed a series of sins of commission, each time doing what God had expressly forbidden: lust, adultery, murder, etc.

On the other hand, Matthew 25:31–46 (especially vv. 41–46) highlight sins of omission, in which the “cursed” fail to do the right thing. The parable of the Good Samaritan also focuses in sins of omission, with the priest and the Levite failing to do what God required of them (Luke 10:30–37).

The juxtaposition of sins of commission with sins of omission can be seen in Romans 7:14–20, where Paul speaks of his tendency to do what is not right, while at the same time failing to do what is right.

We so easily fall into the trap of sins of omission—of failing to do what God requires of us. We need to be constantly on guard against this temptation.Practically, we should deliberately practice doing what is right at all times. As Paul said, “let us not grow weary of doing good, for in due season we will reap, if we do not give up” (Galatians 6:9). It is when we “give up” deliberately doing what is right that we fall into sins of omission.

We should also note that it is possible to commit sin in ignorance.God specifically prescribed sacrifices in the Old Testament for sins committed in ignorance. We must therefore conclude that doing what is wrong is always wrong and we cannot plead ignorance. The Bible holds God’s people accountable for their sins of ignorance (Acts 3:17; 1 Peter 1:14; etc.).

The Christian who understands the heinousness of sin will recognise that the correct way to deal with it is by confession and repentance. David modelled this in Psalm 51 after his sin with Bathsheba. Confession and repentance always secure God’s forgiveness, though this does not necessarily mean that the consequences of the sin are removed. Second Samuel 12:14–15 gives an example of the consequences that David faced despite the fact that God forgave his sin.