Essays collected in this volume deal with various problems from the philosophy of mathematics. What connects them are two questions: how mathematics is created and how it is acquired. In ‘Three Worlds of Mathematics’ we are familiarized with David Tall’s ideas pertaining to the embodied, symbolic, and formal worlds of mathematics. In ‘Basic Ideas of Intuitionism, ’ we focus on an epistemological approach to mathematics which is distinctive to constructive mathematics. The author focuses on the computational content of intuitionistic logic and shows how it relates to functional programming. ‘The Brave Mathematical Ant’ carefully selects mathematical puzzles related to teaching experiences in a way that the solution requires creativity and is not obtainable by following an algorithm. Moreover the solution gives us some new insight into the underlying idea. ‘Degrees Of Accessibility Of Mathematical Objects’ discusses various criteria which can be used to judge accessibility of mathematical objects. We find logical complexity, range of applications, existence of a physical model, as well as aesthetic values.