The general theory of function algebras. Here Bishop worked on uniform algebras proving results such as antisymmetric decomposition of a uniform algebra, the Bishop–DeLeeuw theorem, and the proof of existence of Jensen measures. Bishop wrote a 1965 survey "Uniform algebras," examining the interaction between the theory of uniform algebras and that of several complex variables.
Banach spaces and operator theory, the subject of his thesis. He introduced what is now called the Bishop condition, useful in the theory of decomposable operators.
Constructive mathematics. Bishop became interested in foundational issues while at the Miller Institute. His now-famous Foundations of Constructive Analysis aimed to show that a constructive treatment of analysis is feasible, something about which Weyl had been pessimistic. A 1985 revision, called Constructive Analysis, was completed with the assistance of Douglas Bridges.
In 1972, Bishop published Constructive Measure Theory. In the later part of his life Bishop was seen as the leading mathematician in the area of constructive mathematics. In 1966 he was invited to speak at the International Congress of Mathematics on constructive mathematics. His talk was titled "The Constructivisation of Abstract Mathematical Analysis." The American mathematical society invited him to give four hour-long lectures as part of the Colloquium Lectures series. The title of his lectures was "Schizophrenia of Contemporary Mathematics." Robinson wrote of his work in constructive mathematics: "Even those who are not willing to accept Bishop's basic philosophy must be impressed with the great analytical power displayed in his work." Robinson wrote in his review of Bishop's book that Bishop's historical commentary is "more vigorous than accurate".
Quotes
"Mathematics is common sense";
"Do not ask whether a statement is true until you know what it means";
"A proof is any completely convincing argument";
"Meaningful distinctions deserve to be preserved".
"The primary concern of mathematics is number, and this means the positive integers.... In the words of Kronecker, the positive integers were created by God. Kronecker would have expressed it even better if he had said that the positive integers were created by God for the benefit of man. Mathematics belongs to man, not to God. We are not interested in properties of the positive integers that have no descriptive meaning for finite man. When a man proves a positive integer to exist, he should show how to find it. If God has mathematics of his own that needs to be done, let him do it himself."
"We are not contending that idealistic mathematics is worthless from the constructive point of view. This would be as silly as contending that unrigorous mathematics is worthless from the classical point of view. Every theorem proved with idealistic methods presents a challenge: to find a constructive version, and to give it a constructive proof."
"Theorem 1 is the famous theorem of Cantor, that the real numbers are uncountable. The proof is essentially Cantor's 'diagonal' proof. Both Cantor's theorem and his method of proof are of great importance."
"The real numbers, for certain purposes, are too thin. Many beautiful phenomena become fully visible only when the complex numbers are brought to the fore."
"It is clear that many of the results in this book could be programmed for a computer, by some such procedure as that indicated above. In particular, it is likely that most of the results of Chaps. 2, 4, 5, 9, 10, and 11 could be presented as computer programs. As an example, a complete separable metric spaceX can be described by a sequence of real numbers, and therefore by a sequence of integers, simply by listing the distances between each pair of elements of a given countable dense set.... As written, this book is person-oriented rather than computer-oriented. It would be of great interest to have a computer-oriented version."
"Very possibly classical mathematics will cease to exist as an independent discipline"
"Brouwer's criticisms of classical mathematics were concerned with what I shall refer to as 'the debasement of meaning