Critic

That part of logic, that is, of logica docens, which, setting out with such assumptions as that every assertion is either true or false, and not both, and that some propositions may be recognized to be true, studies the constituent parts of arguments and produces a classification of arguments such as is above described, is often considered to embrace the whole of logic; but a more correct designation is Critic (Greek {kritiké}. According to Diogenes Laertius, Aristotle divided logic into three parts, of which one was {pros krisin}). This word, used by Plato (who divides all knowledge into epitactic and critic), was adopted into Latin by the Ramists, and into English by Hobbes and Locke. From the last it was taken into German by Kant, who always writes it Critik, the initial c being possibly a reminiscence of its English origin. At present it is written Kritik in German. Kant is emphatic in the expression of the wish that the word may not be confounded with critique, a critical essay (German Kritik).

That our thoughts are signs is an old and familiar doctrine. I show that it is only in so far as thoughts are signs, and particularly […] symbols, that they become subjects of logic; and further that the rules of logic are applicable to all symbols. Accordingly by regarding logic as a science of signs or formal semeiotic, and in the main as a science of symbols, or formal symbolic, we accurately cover its subject matter, and at the same time insure ourselves against all risk of being led astray into psychology. The word formal, in this connection, signifies that only the general conditions to which signs ought to conform are to be considered.

But those conditions may be distinguished into three kinds, leading to a corresponding distinction between three departments of logic, in its wider sense; or Formal Semeiotic. Namely the conditions are either, first, such as must be fulfilled in order that an object may be a sign at all; second, such as must be fulfilled in order that the sign may refer to the object to which it aims to refer, that is, may be true; and third, such as must be fulfilled in order that the sign may determine the interpretant it aims to determine, that is, may be pertinent. [—] The study of the second series of conditions is Logic in its narrow sense, or, as we may call it, Critical Logic.

All thought being performed by means of signs, logic may be regarded as the science of the general laws of signs. It has three branches: (1) Speculative Grammar, or the general theory of the nature and meanings of signs, whether they be icons, indices, or symbols; (2) Critic, which classifies arguments and determines the validity and degree of force of each kind; (3) Methodeutic, which studies the methods that ought to be pursued in the investigation, in the exposition, and in the application of truth. Each division depends on that which precedes it.

Logic, which began historically, and in each individual still begins, with the wish to distinguish good and bad reasonings, develops into a general theory of signs. Its three departments are the physiological, or Speculative Grammar; its classificatory part, judging particularly what reasoning is good and what bad, or Logical Critic; and finally, Methodeutic, or the principles of the production of valuable courses of research and exposition.

[Methodeutic] is not possible until the logician has first examined all the different elementary modes of getting at truth and especially all the different classes of arguments and has studied their properties so far as these properties concern power of the arguments as leading to the truth. This part of logic is called Critic.

The second part [of logic], which classifies reasonings and determines their value, received from the eminent English logician, Hobbes, and from the great English philosopher, Locke, the very appropriate name critic.

… a speculative rhetoric, the science of the essential conditions under which a sign may determine an interpretant sign of itself and of whatever it signifies, or may, as a sign, bring about a physical result. [—]
In the Roman schools, grammar, logic, and rhetoric were felt to be akin and to make up a rounded whole called the trivium. This feeling was just; for the three disciplines named correspond to the three essential branches of semeiotics, of which the first, called speculative grammar by Duns Scotus, studies the ways in which an object can be a sign; the second, the leading part of logic, best termed speculative critic, studies the ways in which a sign can be related to the object independent of it that it represents; while the third is the speculative rhetoric …

The function of logic, in its critical part, is to criticize the connection between premisses and conclusions.

The highest kind of symbol is one which signifies a growth, or self-development, of thought, and it is of that alone that a moving representation is possible; and accordingly, the central problem of logic is to say whether one given thought is truly, i.e., is adapted to be, a development of a given other or not. In other words, it is the critic of arguments. Accordingly, in my early papers I limited logic to the study of this problem. But since then, I have formed the opinion that the proper sphere of any science in a given stage of development of science is the study of such questions as one social group of men can properly devote their lives to answering; and it seems to me that in the present state of our knowledge of signs, the whole doctrine of the classification of signs and of what is essential to a given kind of sign, must be studied by one group of investigators. Therefore, I extend logic to embrace all the necessary principles of semeiotic, and I recognize a logic of icons, and a logic of indices, as well as a logic of symbols; and in this last I recognize three divisions: Stecheotic (or stoicheiology), which I formerly called Speculative Grammar; Critic, which I formerly called Logic; and Methodeutic, which I formerly called Speculative Rhetoric.

The whole discussion of the logical nature of the different kinds of possible signs makes up the first division of logic, or Speculative Grammar. The second division, Critic, discusses the relation of signs to their objects, that is, their truth. The third division, Methodeutic, discusses the relations of signs to their interpretants, that is, their knowledge-producing value.

In my view, logic has three parts, 1^st the Elements which makes analysis of what one has to deal with; Arguments &c. 2^nd Critic, which examines the conditions of the validity of arguments, and 3^rd Methodeutic, which shows how any inquiry ought to be conducted.

… my doctrine of Logical Critic [—] I recognize two other parts of Logic. One which may be called Analytic examines the nature of thought, not psychologically but simply to define what it is to doubt, to believe, to learn, etc., and then to base critic on these definitions is my real method, though in this letter I have taken the third branch of logic, Methodeutic, which shows how to conduct an inquiry. This is what the greater part of my life has been devoted to, though I base it upon Critic.

[“Logical Critic”] discusses the justification of each of the essentially different kinds of reasoning…

Semeiotics has three parts: Speculative Grammar, which studies the essential nature of the different kinds of signs; Critic, which studies the general conditions of their relations to their objects; and Methodeutic, which studies the general conditions of their fulfilling their purposes.