Catherine of Siena had an unusual method for avoiding the deadly sin of gluttony. She steered clear of food at all costs other than the odd herb (she died of starvation, aged 33) but if she had to nourish herself with something more substantial, she would put her mouth to the putrefying sore of a plague victim and gulp down the pus. For the pus-slurping saint, nothing tasted ‘sweeter or more exquisite’. Catherine believed it combined the two most powerful religious principles, ‘service’ and ‘suffering’; the former in cleaning the wound and the latter need hardly be spelled out.

This is an extreme example of the lengths to which medieval men and women went to avoid committing any of the seven deadly sins. In this wonderful, eye-opening book, historian Peter Jones guides us through pride, envy, anger, sloth, avarice, gluttony and lust, showing what they meant to ordinary (and some not so ordinary) people. Outside of pus-drinking, Jones manages to make an excellent argument for how keeping these sins in the back of your mind can be an effective tool to living a good life, even in the 21st century.

Before therapists, medieval folk had priests, and instead of diagnoses, they had the seven deadly sins. If you found yourself mired in sloth for example, then there were countless medieval spiritual guidebooks to help you get back on track.

When Jones took a teaching post in Siberia, he was cold, lonely and soon fell into a pit of depression. As a medieval obsessive, he began to notice how easy it would be to slip into feeling consumed by the sins, and managed to claw his way back to contentment using medieval advice. There is a healthy dose for each of the sins. Envy can be a useful emotion if it makes you notice the things that would make you happier in life, such as another job. Jones, for instance, was envious of a friend’s teaching post in California, which seems perfectly justified. Envy only becomes poisonous to the soul when it turns into a desire to watch people fail, while blinding us to the good fortune we may already have.

According to a 13th century guidebook, the way to avoid this is to ‘modify our attention’ and rather than delighting in someone’s failures, try to ‘rejoice in every triumph of our rival’. After this, ‘we’ll find our envy can wash into compassion’. Excellent advice, even 800 years on!

Lust, interestingly, is the least deadly, as it is fundamentally about connecting with another human. However, when this slips into treating someone as an object to satisfy your urges, then you may have tripped and fallen into committing a deadly sin. Want to cure this? Take Bernard of Clairvaux’s advice and hold firm to your lustful feelings but simply redirect them to ‘consummation in the spirit’ or communion with Jesus.

Some (possibly repressed) women took this advice to heart (and to other organs too). Angela of Foligno had a habit of stripping naked in front of the cross to feel connected to Christ. Once she felt an inner fire ‘so hot’ that she decided she ‘had no choice but to overpower this burning insatiable lust’ so grabbed a candle and put it ‘straight to her genitals’.

Jones is brilliant company and a wonderful teacher who can smoothly guide one through the often bewildering world of the Middle Ages. If taking medieval advice is at all responsible for the affable character of this delightful historian, then no doubt we should all be following his example and looking to the middle ages for a daily dose of self help.