The Commens Dictionary

Quote from ‘Minute Logic: Chapter II. Prelogical Notions. Section I. Classification of the Sciences (Logic II)’


Among the theoretical sciences [of discovery], I distinguish three classes, all resting upon observation, but being observational in very different senses. [—]

Class III is Bentham’s idioscopic [CP 1.242n2: “Idioscopic … from two Greek words, the first of which signifies peculiar. In Idioscopic ontology, then, we have that branch of art and science which takes for its subject such properties as are considered as peculiar to different classes of beings, some to one such class, some to another.” The Works of Jeremy Bentham, Edinburgh, 1843, viii, 83, footnote.]; that is, the special sciences, depending upon special observation, which travel or other exploration, or some assistance to the senses, either instrumental or given by training, together with unusual diligence, has put within the power of its students. This class manifestly divides itself into two subclasses, the physical and the psychical sciences; or, as I will call them, physiognosy and psychognosy. Under the former is to be included physics, chemistry, biology, astronomy, geognosy, and whatever may be like these sciences; under the latter, psychology, linguistics, ethnology, sociology, history, etc. Physiognosy sets forth the workings of efficient causation, psychognosy of final causation.

CP 1.239-242
‘Idioscopy’ (pub. 07.04.13-16:43). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from
Apr 07, 2013, 16:43 by Sami Paavola
Last revised: 
Jan 07, 2014, 00:58 by Commens Admin