The best excuse? Blame someone else ...

"A successful excuse needs to make plausible that your intention really was morally adequate - but something beyond your control prevented you from translating it into action." Photo / 123RF

Whether you are late for work or have forgotten a friend's birthday, crafting the perfect excuse is an art we all strive to master.

Now, a Cambridge academic has discovered the best way to get yourself off the hook is to blame someone, or something, else.

Dr Paulina Sliwa, an expert in moral psychology and philosophy of mind at Cambridge's Faculty of Philosophy, has created the first "unified theory of excuses", which she calls the Good Intention Account.

Her study, published in the journal Philosophy & Public Affairs, argues that the most effective excuses are those where you explain that you had the right intentions, but were thwarted by circumstances beyond your control.

If you wanted to apologise for forgetting an appointment, examples of this approach might include "I had a terrible migraine" or "I haven't slept for the last three nights" or "I was preoccupied with worries about my mother's health".

Or, if you wanted to apologise for breaking a vase, you might say "I stumbled over the rug".

Dr Sliwa explained: "A successful excuse needs to make plausible that your intention really was morally adequate - but something beyond your control prevented you from translating it into action. They all indicate an adequate underlying moral motivation that was thwarted by external circumstances."

Dr Sliwa explains how everyday excuses work in much the same way as those offered in a courtroom. When lawyers claim duress or provocation in defence of their client, they are saying the client may have broken the law but had a morally adequate intention.

Excuses that "never work" involve weakness of will, such as "I just couldn't resist" or "it was too tempting", the study found.

"Nor do appeals to things that are obviously immoral," Dr Sliwa said.

"The same is true of legal excuses: not every appeal to duress, coercion or provocation will be successful - it will depend on the details of the case."

However, there is a limit to how far excuses will get you.

"Successful excuses can mitigate our blame, but they don't get us off the hook completely," she said.

"Saying we were tired or stressed doesn't absolve us from moral responsibility completely, though they do change others' perceptions of what we owe to make up for it and how the offended party should feel about our wrongdoing."