One of the most fundamental concepts in Hesychasm is the ‘tempting thought’ (from the Greek, λογισμός or ‘thought’). Mental ascesis is the practice of refusing tempting thoughts. This mental ascesis is ordinarily practised with the mind in the heart and in coordination with the repetition of the Jesus Prayer. The goal is to attain to a practice of the Jesus Prayer in which the mind is in the heart and free of images. This practice of the Jesus Prayer in the heart free from images is called the ‘guard of the mind’. It is a state of peace. It is a drinking from the silence of God.
A ‘tempting thought’ is a thought that invites us to one of the eight sins. It begins with the formation in the mind of an image of a sensible object. When the image of a sensible object arises in our mind, we ‘converse’ with the image, which invites us to partake of the sin that the image suggests. Hence, the notion of the tempting thought. ‘The temptation of the monk is the thought that arises from the passionate part of the soul and darkens the mind; the sin of the monk is the consent to the forbidden pleasure that the thought suggests.’ (Evagrius.) That is why in the guard of the mind there are no images in the mind, only the repetition of the Jesus Prayer: the monk has been purified of the tendencies to sin in him and immediately refuses any tempting thoughts that come to him. He is now ready to contemplate God and his creation.