We know we are all sinners because Scripture clearly states that all have sinned and that we inherit this sin nature from Adam (Romans 5:12).
The doctrine of original sin, as explained in Romans 5:12, asserts that sin entered the world through Adam, and as a result, death passed upon all men because all have sinned. This means that every person born into the world inherits a sinful nature, and thus, we are all accountable for our own personal sins as well. 1 John 1:8 emphasizes that denying our sinfulness is a self-deception, while Proverbs 20:9 questions who can say they are pure. The biblical text illustrates that our propensity to sin manifests not only through actions but also in our thoughts and desires—a comprehensive view of our sinful nature.
Scripture References:
Romans 5:12, 1 John 1:8, Proverbs 20:9
Commentary