As a logician Lotze stands among the masters.
GEORGE BOOLE (1815-1864), English logician and mathematician, was born in Lincoln on the 2nd of November 1815.
GILBERT DE LA PORREE, frequently known as Gilbertus Porretanus or Pictaviensis (1070-1154), scholastic logician and theologian, was born at Poitiers.
Gilbert is almost the only logician of the 12th century who is quoted by the greater scholastics of the succeeding age.
But Gilbert de la Porree, according to Haureau, is the most eminent logician of the Realistic school in the 12th century and the most profound metaphysician of either school.
He had no great tincture of learning, he was by no means a profound logician, and he was impulsive and emotional in the extreme - characteristics which in political matters predispose the subject to the preference of equality above all political requisites.
JOHN WALLIS (1616-1703), English mathematician, logician and grammarian, was born on the 23rd of November 1616 at Ashford, in Kent, of which parish his father, Rev. John Wallis (1567-1622), was incumbent.
In the Categories he classified names, not, however, as a grammarian by their structure, but as a logician by their signification.
Hence the manner in which induction aided by identification discovers necessary principles must be studied by the logician in order to decide when the syllogism can really arrive at necessary conclusions.
But there is an intermediate alternative, which is neither impossible nor arbitrary; namely, to consider the general distinctions and principles of all things; and without this general consideration of the matter the logician cannot know the form of thought, which consists in drawing inferences about things on these general principles.
It is clear then that a man's metaphysics and psychology must colour his logic. It is accordingly necessary to the logician to know beforehand the general distinctions and principles of things in metaphysics, and the mental operations of sense, conception, memory and experience in psychology, so as to discover the processes of inference from experience about things in logic.
But how little does the psychologist know about the association of ideas, compared with what the logician has discovered about the processes of inference!
Logic has to consider the things we know, the minds by which we know them from sense, memory and experience to inference, and the sciences which systematize and extend our knowledge of things; and having considered these facts, the logician must make such a science of inference as will explain the power and the poverty of human knowledge.
It is a matter of words whether or not we should call this sensory belief a judgment; but it is no matter of choice to the logician, who regards all the constituents of inference as judgments; for the fundamental constituents are sensory beliefs, which are therefore judgments in the logical sense.
The two are complementary, and the reinstatement of the disjunctive judgment to the more honourable role in inference has been made by so notable a modern logician as Lotze.
It was because the aftermath of Newtonian science was so rich that the scientific faith of naturalism was able to retain a place besides its epistemological creed that a logician of the school could arise whose spirit was in some sort Baconian, but who, unlike Bacon, had entered the modern world, and faced the problems stated for it by Hume and by Newton.
Directly he affected a school of thought which contained one logician of first-rate importance in Moritz Wilhelm Drobisch (1802-1896), professor at Leipzig.
Yet it is in the detail of his logical investigations, something too volatile to fix in summary, that Lotze's greatness as a logician more especially lies.
The System der Logik (1828) of Bachmann (a Kantian logician of distinction) contains a historical survey (pp. 569-644), as does the Denklehre (1822) of van Calker (allied in thought to Fries), pp. 12 sqq.; Eberstein's Geschichte der Logik and Metaphysik bei den Deutschen von Leibniz bis auf gegenwartige Zeit (latest edition, 1 799) is still of importance in regard to logicians of the school of Wolff and the origines of Kant's logical thought.
BURGERSDYK or Burgersdicius, Francis (1590-1629), Dutch logician, was born at Lier, near Delft, and died at Leiden.
He was a prolific writer, and at the time of his death he occupied the foremost position in England both as a logician and as an economist.
AUGUSTUS DE MORGAN (1806-1871), English mathematician and logician, was born in June 1806, at Madura, in the Madras presidency.
Wide as Bain's influence has been as a logician, a grammarian and a writer on rhetoric, his reputation rests on his psychology.
But as yet he had given no sign of system, and-what is surprisingno trace of logic. Aristotle was primarily a metaphysician against Plato; a metaphysician before he was a logician; a metaphysician who made what he called primary philosophy pd.Yrri 4aXocr00La) the starting-point of his philosophical development, and ultimately of his philosophical system.
It is nearer to Plato's analysis of the sentence, and no logician would have gone back to it, after the Prior Analytics.
He gradually became a logician out of his previous studies: out of metaphysics, for with him being is always the basis of thinking, and common principles, such as that of contradiction, are axioms of things before axioms of thought, while categories are primarily things signified by names; out of the mathematics of the Pythagoreans and the Platonists, which taught him the nature of demonstration; out of the physics, of which he imbibed the first draughts from his father, which taught him induction from sense and the modification of strict demonstration to suit facts; out of the dialectic between man and man which provided him with beautiful examples of inference in the Socratic dialogues of Xenophon and Plato; out of the rhetoric addressed to large audiences, which with dialectic called his attention to probable inferences; out of the grammar taught with rhetoric and poetics which led him to the logic of the proposition.
It is the business of the logician to find the causes of the judgments which form the premises and the conclusions of inference, reasoning and science.
Had Bacon analysed bodies into their elements, instead of their qualities and ways of behaviour, he would have been the logician of the chemical formula.
The psychologist and the formal logician do indeed join hands in the denial of a real movement of thought in syllogism.
WILLIAM STANLEY JEVONS (1835-1882), English economist and logician, was born at Liverpool on the 1st of September 1835.
His strength lay in his power as an original thinker rather than as a critic; and he will be remembered by his constructive work as logician, economist and statistician.
Moreover we commonly find the logician assuming that the process of thought has advanced a certain length before his examination of it begins; he takes his material full-formed from perception, without, as a rule, inquiring into the nature of the conceptions which are involved in our perceptive experience.