# XXXII explained — Philosophical Works > Chapter companion for Philosophical Works by René Descartes. ## What happens Descartes distinguishes two fundamental modes of thinking: perception (understanding) and volition (will). All mental acts—sensing, imagining, conceiving—are forms of perception, while desiring, avoiding, affirming, denying, and doubting are forms of willing. ## Themes in this chapter ### Mind-Body Dualism By categorizing all modes of thinking into perception and will, Descartes reinforces the primacy of mental operations over bodily sensations. ### Reason and Method The clear classification of mental acts exemplifies Descartes' methodical approach to understanding the mind's operations. ## Character check-ins ### Narrator Presents the classification of thought into perception and will. ### René Descartes Author of the distinction between understanding and will. ## Key lines > For all the modes of thinking of which we are conscious may be referred to two general classes, the one of which is the perception or operation of the understanding, and the other the volition or operation of the will. Every conscious thought belongs to one of two categories: perception (an act of understanding) or volition (an act of will). _Descartes establishes a fundamental dichotomy in the nature of thought._ > Thus, to perceive by the senses ( sentire ), to imagine, and to conceive things purely intelligible, are only different modes of perceiving ( percipiendi ); but to desire, to be averse from, to affirm, to deny, to doubt, are different modes of willing. Sensing, imagining, and understanding are all forms of perception; while desiring, avoiding, affirming, denying, and doubting are all forms of willing. _Concrete examples clarify the two classes of mental activity._ ## Links - HTML: https://www.betterreads.online/discover/philosophical_works_se/chapters/xxxii - Book: https://www.betterreads.online/discover/philosophical_works_se - All chapters: https://www.betterreads.online/discover/philosophical_works_se/chapters