I want to understand what the sin of acedia is, and what the remedies for it are. I would also welcome any reading suggestions.
Acedia is one of the seven cardinal sins, which means that it is not only a sin, but a cause of other sins. The term acedia is usually translated “sloth,” which makes it seem like laziness. This is a bit misleading, because the disinclination to make any spiritual or moral effort is only a symptom of sloth, not its essence. Its root is an “oppressive sorrow which so weighs upon man’s mind that he wants to do nothing,” a "sluggishness of the mind which neglects to begin good." For this reason, sloth is also called tristitia, or sadness. This is important: Sadness is not wrong in itself. However, it is wrong to neglect what is good because of sadness, and we have a moral duty not to wallow in such sadness, but to try to resist it.
The problem does not lie not in sorrow which is fitting due to loss, for it is right to grieve sometimes. Nor does the problem lie in that good sorrow which prompts us to change our ways when we have been in error. Nor does it lie in despondency which is beyond our control because there is something wrong with our body chemistry. Rather it lies in a voluntary and habitual tendency to indulge in excessive sadness in a way which withdraws us from good, especially spiritual good.
Thomas Aquinas explains how sloth gives rise to other vices too: “Just as we do many things on account of pleasure, both in order to obtain it, and through being moved to do something under the impulse of pleasure, so again we do many things on account of sorrow, either that we may avoid it, or through being exasperated into doing something under pressure thereof.” For example, I may dissipate myself in all sorts of worthless activity just to avoid doing what I should do.
Even good sorrow becomes bad when we allow it to overpower and master us. I may be so swallowed up in sorrow for my repented and forgiven sins that I am drawn away from doing good. I may be so disappointed by my moral weakness that I stop trusting God. I may be so distraught about the brokenness of the world, or the times, that I abandon myself to despair. It is even possible to be grieved about good itself -- just because it involves doing work. For example, I may turn away from the good of charity, because it requires me to take care of my ailing wife or father.
Reading suggestions? My quotations have been from Thomas Aquinas, who discusses sloth here. However, a number of Thomists have written on the virtues and vices. One of the finest writers on the topic is the great Josef Pieper, whom I highly recommend. If you want to check out my own work, I’ve tried to put sloth in the context of the virtues and vices in my Commentary on Thomas Aquinas’s Virtue Ethics. Reading an earlier draft of this post, an acquaintance recommended to me two recent books just about acedia, so you may want to investigate those too: Jean-Charles Nault, The Noonday Devil, and R.J. Snell, Acedia and its Discontents.
Remedies? Probably the best remedies for the sin of sloth are work, prayer, and caring for others. By caring for others, I mean both corporal and spiritual acts of mercy.
Although those are the most important, the remedies for ordinary sadness may also be helpful. What these are will come as no surprise. St. Thomas suggests pleasant recreation and playfulness, from which we see that the remedy of work can be overdone: “Man's mind would break if its tension were never relaxed.” He also suggests shedding a few tears, accepting the sympathy of friends, contemplating the great truths of faith, and even having a warm bath and sleeping -- so long as one does not use these things as new excuses to do nothing!
By the way, concerning the contemplation of the truths of faith as a remedy for sloth, one is especially helpful. This is the fact that Christ took the worst of our burdens upon Himself, including loneliness, pain, and death. The meaning of the Cross is not defeat, but victory over these things – victory through submitting to them. And thus, whatever our sufferings, by God’s grace they can join us more closely to Him. By doing the work that He gives us, and not wallowing in sorrows, but accepting them for His sake, we imitate Him.
To this truth of faith, we may add a truth of philosophy – a preamble to faith. This is the fact that even the occasional feeling of meaninglessness is a sign of meaning. For consider: If we were merely evolved mud, we would not suffer such feelings at all. Quite the opposite, because in that case we would be perfectly adapted to a meaningless world. The fact that we do long for more is a sign of the loving God who made us for more. So even our tears are grounds to rejoice.