Week after week after week. The Secret is persistently amongst the top ten non-fiction (I use the word advisedly) bestsellers. Why? What's with this small tome of esoteric self-help advice? I stole a look in a bookshop. And William James provided the key to unlock the secret of The Secret.

It's an example of what he called a 'mind cure', and he'd noticed a variety of mind cure movements growing in the quarter century before he gave his lectures on The Varieties of Religious Experience - which is to say that they emerged in the nineteenth century. The essential doctrine that links an otherwise diverse philosophy is that thoughts are things. So to change your thoughts is to change things as they are in the world.

That is linked to a dominant optimism - and it attracts individuals with an optimistic temperament, particularly those to whom doctrines like Christianity's original sin, or psychoanalysis's dark unconscious, seem ugly and pessimistic. That, it turns out, is a lot of people, hence the success of the various forms of mind cure - which range from the power of positive thinking, through Christian Science, to more scientifically informed versions like CBT.

The Secret appears to be just a simplified form of this mental hygiene: if your thoughts are of health or insight or wealth then before you know it, you will receive health or insight or wealth. (Similarly, to think you are ill or ill-fated is simply not to be thinking right: you are well, and will know it.) It's believed this happens because of a universal law that like attracts like. And, if you align yourself to the benign flux of life, then things can only go well.