Because what God so severely punished must have been no light sin but a detestable crime, we must consider what species of sin (peccati) there was in Adam’s fall that kindled God’s horrible vengeance against the whole human race. To regard Adam’s sin as gluttonous intemperance (a common notion) is childish. As if the sum and head of all virtues lay in abstaining solely from one fruit, when all sorts of desirable delights abounded everywhere; and not only abundance but also magnificent variety was at hand in that blessed fruitfulness of earth!
We must, therefore, look deeper. The prohibition from the tree of knowledge of good and evil was a test of obedience (obedientiae examen), that Adam, by observing it, might prove his willing submission to the command of God. The very name of the tree shows the sole purpose of the precept was to keep him content with his lot and to prevent him from becoming puffed up with cupidity. The promise (promissio), which gave him hope of eternal life as long as he should eat of the tree of life (arbore vitae), and, on the other hand, the fearful denunciation of death the moment he should taste of the tree of knowledge of of good and evil, were meant to test (probandam) and exercise his faith. Hence it is not hard to deduce by what means Adam provoked God’s wrath upon himself. Indeed, Augustine speaks rightly when he declares that pride was the beginning of all evils. For if ambition had not raised man higher than was meet and right, he could have remained in his original state.
—John Calvin, Institutes, 2.1.4.
(“… taste of the tree of knowledge of of good and evil …” – poor John is stuttering again) For many years I misunderstood the phrase to mean the ability to differentiate what is good from that which is evil. Adam did not need to eat of the fruit to have that ability. The meaning of the phrase includes the experiential/experimental knowledge of both good and evil – The earliest fare to be found at the table of demons was this fruit. One could coin the word “Profanament” to denote this evil counterpart of the Sacrament.