In The Philosophy of Cognitive-Behavioural Therapy, Donald Robertson cites "the influence of the Stoic tradition" on the writings of the 20th century philosopher Bertrand Russell. Robertson goes on to cite The Conquest of Happiness (1930) in which Russell describes "a philosophical method of overcoming anxiety and worry, indistinguishable from the praemeditatio malorum" as well as what Robertson calls "one of the most lucid explanations of exposure therapy that one could wish for:
Worry is a form of fear, and all forms of fear produce fatigue. A man who has learnt not to feel
fear will find the fatigue of daily life greatly diminished. Now fear, in its most basic harmful form
arises where there is some danger which we are unwilling to face. At odd moments horrible
thoughts dart into our minds; what they are depends upon the person, but almost everybody has
some kind of lurking fear. [Russell, 1930, p.60]"
Robertson goes on to describe Russell's prescription that "the proper course with every kind of fear is to think about it rationally and calmly, but with great concentration, until it becomes completely familiar. In the end its familiarity will blunt its terrors; the whole subject will become boring, and our thoughts will turn away from it, not, as formerly, by an effort of will, but through a mere lack of interest in the topic."