Digital Companion to C. S. Peirce
1895 [c.] | On Quantity, with special reference to Collectional and Mathematical Infinity | NEM 4:273

Philosophy, which makes no special observations, but uses facts commonly known. In order to be exact, it must rest on mathematical principles. It divides into Logic, which studies the world of thought, and Metaphysics, which studies the world of being; and the latter must rest upon the principles of the former.

1895-6 [c.] | That Categorical and Hypothetical Propositions are one in essence, with some connected matters | MS [R] 787:5

There are […] observations which are not only open to all men; but which are necessarily open to all intelligences capable of acquiring scientific, imperfect knowledge from observation and reasoning. The science which is base on such observations as these may suitably be called philosophy. This science will be somewhat narrower than what is commonly called philosophy, since it will exclude ethics, esthetics, etc. which repose on observations which might be foreign to some kind of scientific mind. This science of philosophy, although it is observational, yet will have, in a certain sense, a necessary character; for it is based exclusively on such observations as must be open to every scientific intelligence.

1896 | On the Logic of Quantity | MS [R] 13:1-2

The second prime division of the sciences consists of Philosophy, which concerns itself, indeed, with positive truths but only with such as would manifestly remain true whatever observation might reveal. Even if it be denied that there is any such truth, a place in the scheme of the sciences must be accorded to this inquiry. For a department of science is not a body of truth but a group of possible researches after truth.

1898 | Cambridge Lectures on Reasoning and the Logic of Things: Philosophy and the Conduct of Life | EP 2:36

Philosophy seems to consist of two parts, Logic and Metaphysics. I exclude Ethics, for two reasons. In the first place, as the science of the end and aim of life, [ethics] seems to be exclusively psychical, and therefore to be confined to a special department of experience, while philosophy studies experience in its universal characteristics. In the second place, in seeking to define the proper aim of life, ethics seems to me to rank with the arts, or rather with the theories of the arts, which of all theoretical sciences I regard as the most concrete, while what I mean by philosophy is the most abstract of all the real sciences.

1902 | Minute Logic: Chapter II. Prelogical Notions. Section I. Classification of the Sciences (Logic II) | CP 1.239-241

Among the theoretical sciences [of discovery], I distinguish three classes, all resting upon observation, but being observational in very different senses.
Class II is philosophy, which deals with positive truth, indeed, yet contents itself with observations such as come within the range of every man’s normal experience, and for the most part in every waking hour of his life. Hence Bentham calls this class, coenoscopic. [CP 1.241n1: “Coenoscopic … from two Greek words, one of which signifies common – things belonging to others in common; the other looking to. By coenoscopic ontology, then, is designated that part of the science which takes for its subject those properties which are considered as possessed in common by all the individuals belonging to the class which the name ontology is employed to designate, i.e. by all individuals.” The Works of Jeremy Bentham, Edinburgh, 1843, viii, 83, footnote.] These observations escape the untrained eye precisely because they permeate our whole lives, just as a man who never takes off his blue spectacles soon ceases to see the blue tinge. Evidently, therefore, no microscope or sensitive film would be of the least use in this class. The observation is observation in a peculiar, yet perfectly legitimate, sense. If philosophy glances now and then at the results of special sciences, it is only as a sort of condiment to excite its own proper observation.
Next, passing to Class II, philosophy, whose business it is to find out all that can be found out from those universal experiences which confront every man in every waking hour of his life, must necessarily have its application in every other science. For be this science of philosophy that is founded on those universal phenomena as small as you please, as long as it amounts to anything at all, it is evident that every special science ought to take that little into account before it begins work with its microscope, or telescope, or whatever special means of ascertaining truth it may be provided with.

1902 [c.] | Peirce's Personal Interleaved Copy of the 'Century Dictionary' [Commens] | CP 5.13 n.1

Philosophy is that branch of positive science (i.e., an investigating theoretical science which inquires what is the fact, in contradistinction to pure mathematics which merely seeks to know what follows from certain hypotheses) which makes no observations but contents itself with so much of experience as pours in upon every man during every hour of his waking life. The study of philosophy consists, therefore, in reflexion…

1903 | A Syllabus of Certain Topics of Logic | CP 1.183-186

Science of Discovery is either, I. Mathematics; II. Philosophy; or III. Idioscopy.

Mathematics studies what is and what is not logically possible, without making itself responsible for its actual existence. Philosophy is positive science, in the sense of discovering what really is true; but it limits itself to so much of truth as can be inferred from common experience. Idioscopy embraces all the special sciences, which are principally occupied with the accumulation of new facts.
Philosophy is divided into a. Phenomenology; b. Normative Science; c. Metaphysics.

1903 | Harvard Lectures on Pragmatism: Lecture II | CP 5.61

Philosophy, as I understand the word, is a positive theoretical science, and a science in an early stage of development. As such it has no more to do with belief than any other science. Indeed, I am bound to confess that it is at present in so unsettled a condition, that if the ordinary theorems of molecular physics and of archaeology are but the ghosts of beliefs, then to my mind, the doctrines of the philosophers are little better than the ghosts of ghosts. I know this is an extremely heretical opinion.

1904 | A Brief Intellectual Autobiography by Charles Sanders Peirce | Peirce, 1983, p. 70; MS [R] L107:18

Philosophy merely analyzes the experience common to all men. The truth of this experience is not an object of an science because it cannot really be doubted.

1904 | Reason's Conscience: A Practical Treatise on the Theory of Discovery; Wherein logic is conceived as Semeiotic | NEM 4:191; HP 2:825

Philosophy is that science which limits itself to finding out what it can from ordinary everyday experience, without making any special observations.

1905-12-20 | The Logic Notebook | MS [R] 339:267r

“Philosophy” has 2 principal meanings

  1. The cream of the science, – synthetic or positive philosophy
  2. Cenoscopy, the study of the experience already acquired.
1906 | The Basis of Pragmaticism | EP 2:372-3

Two meanings of the term ‘philosophy’ call for our particular notice. The two meanings agree in making philosophical knowledge positive, that is in making it a knowledge of things real, in opposition to mathematical knowledge, which is knowledge of the consequences of arbitrary hypotheses; and they further agree in making philosophical truth extremely general. But in other respects they differ as widely as they well could. For one of them, which is better entitled (except by usage) to being distinguished as philosophia prima than is ontology, embraces all that positive science which rests upon familiar experience and does not search out occult or rare phenomena; while the other, which has been called philosophia ultima, embraces all that truth which is derivable by collating the results of the different special sciences, but which is too broad to be perfectly established by any one of them. The former is well named by Jeremy Bentham’s term cenoscopy […], the latter goes by the name of synthetic philosophy.

1911 | A Logical Critique of Essential Articles of Religious Faith | MS [R] 852:6-7

By Philosophy, I mean that branch of heuretic science (the science of discovery,) which, in the first place, seeks categorical truth, and does not, like mathematics, content itself with demonstrating the truth of its discoveries conditionally upon the absolute acceptance of the exact truth of postulates, conditions, or antecedents, for which that science does not in the least assume responsibility. Yet Philosophy, as I understand it, although it is a heuretic science of categorical truth, […] does not profess either by wider or by more refined observations to open to us any new experience whatever. On the contrary, all that it is to teach us, it is to teach by new reasonings based [on] the common experience of all mankind, or at any rate upon what nobody in the world has any doubt about, or can possibly bring himself to doubt of it.

nd | Philosophy in the Light of the Logic of Relatives | MS [R] 1336:1

Philosophy is the study whose purpose it is to determine what is the rational attitude toward things, in general.

nd | A Suggested Classification of the Sciences | MS [R] 1339:6

I divide the sciences of discovery into, 1, Mathematics, which traces out the consequences of hypotheses without concerning itself with their truth, and as the business is carried on, also formulates these hypotheses to represent in some measure confused statements of supposed fact (or fancy); 2, Philosophy, which deals with positive truth, but only so far as it is discoverable from ordinary everyday experience; 3, Idioscopy, or Special Science, which business chiefly consists in observation.