Bernard Bolzano: Philosophy of Mathematical Knowledge

Bernard Placidus Johann Nepomuk Bolzano was born on 5 October 1781 in Prague. He was the son of an Italian art merchant and of a German-speaking Czech mother. His early schooling was unexceptional: private tutors and education at the lyceum. In the second half of the 1790s, he studied philosophy and mathematics at the Charles-Ferdinand University. He began his theology studies in the Fall of 1800 and simultaneously wrote his first mathematical treatise. When he completed his studies in 1804, two university positions were open in Prague, one in mathematics, the other one in the “Sciences of the Catholic Religion.” 

In Bernard Bolzano’s theory of mathematical knowledge, properties such as analyticity and logical consequence are defined on the basis of a substitutional procedure that comes with a conception of logical form that prefigured contemporary treatments such as those of Quine and Tarski. Three results are particularly interesting: the elaboration of a calculus of probability, the definition of (narrow and broad) analyticity, and the definition of what it is for a set of propositions to stand in a relation of deducibility (Ableitbarkeit) with another. 

The main problem with assessing Bolzano's notions of analyticity and deducibility is that, although they offer a genuinely original treatment of certain kinds of semantic regularities, contrary to what one might expect they do not deliver an account of either epistemic or modal necessity. This failure suggests that Bolzano does not have a workable account of either deductive knowledge or demonstration. Yet, Bolzano’s views on deductive knowledge rest on a theory of grounding (Abfolge) and justification whose role in his theory is to provide the basis for a theory of mathematical demonstration and explanation whose historical interest is undeniable. 

The importance of Bolzano’s contribution to semantics can hardly be overestimated. The same holds for his contribution to the theoretical basis of mathematical practice. Far from ignoring epistemic and pragmatic constraint, Bolzano discusses them in detail, thus providing a comprehensive basis for a theory of mathematical knowledge that was aimed at supporting work in the discipline. As a mathematician, Bolzano was attuned to philosophical concerns that escaped the attention of most of his contemporaries and many of his successors. His theory is historically and philosophically interesting, and it deserves to be investigated further.

17TH CENTURY MATHEMATICS. FERMAT

Another Frenchman of the 17th Century, Pierre de Fermat, effectively invented modern number theory virtually single-handedly, despite being a small-town amateur mathematician. Stimulated and inspired by the “Arithmetica” of the Hellenistic mathematician Diophantus, he went on to discover several new patterns in numbers which had defeated mathematicians for centuries, and throughout his life he devised a wide range of conjectures and theorems. He is also given credit for early developments that led to modern calculus, and for early progress in probability theory.

Although he showed an early interest in mathematics, he went on study law and received the title of councillor at the High Court of Judicature in Toulouse in 1631, which he held for the rest of his life. He was fluent in Latin, Greek, Italian and Spanish, and was praised for his written verse in several languages, and eagerly sought for advice on the emendation of Greek texts.

Fermat's mathematical work was communicated mainly in letters to friends, often with little or no proof of his theorems. Although he himself claimed to have proved all his arithmetic theorems, few records of his proofs have survived, and many mathematicians have doubted some of his claims, especially given the difficulty of some of the problems and the limited mathematical tools available to Fermat.

One example of his many theorems is the Two Square Theorem, which shows that any prime number which, when divided by 4, leaves a remainder of 1 (i.e. can be written in the form 4n + 1), can always be re-written as the sum of two square numbers.

Fermat’s correspondence with his friend Pascal also helped mathematicians grasp a very important concept in basic probability which, although perhaps intuitive to us now, was revolutionary in 1654, namely the idea of equally probable outcomes and expected values.

To know what Fermat's Little Theorem is about, what numbers are watch a video below: