Abstract My thesis is partly historical and partly critical. First, I will lay down a brief overview of Frege’s semantics and ontology based on his major works such as Begriffsschrift, “On Sense and Reference”, “On Concept and Object”, “Thought” and so on. The goal of this part of my research is to get a clear picture of Frege’s system and see what features of it are arbitrary and in those cases what other options exist. Next, I will use the secondary literature to find out how other scholars have interpreted Frege. I intend to use some modern logical tools such as lambda calculus in order to analyze Frege’s views more perspicuously. Then I will draw my conclusions about his ontology and semantics. Frege seems to have believed that we approach the world via thought, but have no access to thought except via language. Hence, his enquiry into the nature of the world was conducted via enquiries into the nature of language. However, he knew that natural language sometimes muddles thought, so he tried to create an artificial formula language that would be able to capture the logical structure of the world itself as it is reflected in thought, better than any natural language. I will discuss the importance and the role of an ideal language in science, and will try to determine from Frege's scattered remarks what characteristics he thinks such a language must have. I will then consider Frege's own formalized language, as first presented in the 1879 Begriffsschrift and as further developed in his later writings. I will then discuss Frege’s semantics, focussing mainly on his theory of multiple analyses and his notion of thought and conceptual content. Finally, I will provide a detailed study of Frege’s theories of identity, in Begriffsschrift and “On Sense and Reference”, that were critical in the development of his semantics and ontology.