The sin of Book I is at first sight more obscure, but it…

““The sin of Book I is at first sight more obscure, but it is particularly significant. We have seen that there appear to be two very important episodes showing the Red-Crosse a prey to Despair. When we find, further, that of the three Paynim Brethren, Sansfoy, Sansloi and Sansjoy, it is the last who is the Red-Crosse's most formidable enemy, we are driven to assume that there is some special significance in this stressing of a tendency to melancholy. Such a tendency is not now regarded as a serious sin, but in mediaeval times melancholy leading to inertia and in extreme cases to suicide was under the name of accidie one of the recognized Deadly Sins. By Elizabeth's day the much less pregnant term Sloth had been substituted in the usual catalogue, and Spenser nowhere uses the word accidie. But the late sixteenth and early seventeenth centuries were much preoccupied with the subject. They regarded the sufferers from it as at once in a highly dangerous spiritual state and as intensely interesting. It was the favourite pose of fashionable young men. Hamlet is the supreme treatment of it in literature, but most of the dramatists of the day are interested in it. I suggest that the first Book of the original Faerie Queene treated of the sin of accidie.””

— Janet Spens