The state therefore to which Adam was reduced by his disobedience, so far as his subjective condition is concerned, was analogous to that of the fallen angels. But the unbelief and disobedience of our first parents brought not only on themselves this misery and ruin, it entailed also the same sad consequences on all their descendants. Hence, also, all his descendants inherit a corrupt nature. In all by nature there is an inherent and prevailing tendency to sin. This universal depravity is taught by universal experience.
All men sin as soon as they are capable of moral actions.
They surely throw some light on that great question, the origin of evil. God has thought fit to allow evil to exist in order that he may have a platform for showing his mercy, grace, and compassion. If man had never fallen there would have been no opportunity of showing divine mercy. But by permitting evil, mysterious as it seems, God's works of grace, mercy, and wisdom in saving sinners have been wonderfully manifested to all his creatures. Without the Fall we should have known nothing of the Cross and the Gospel.