This textbook presents the basics of philosophy that are necessary for the student and researcher in science in order to better understand scientific work. The approach is not historical but formative: tools for semantical analysis, ontology of science, epistemology, and scientific ethics are presented in a formal and direct way. The book has two parts: one with the general theory and a second part with application to some problems such as the interpretation of quantum mechanics, the nature of mathematics, and the ontology of spacetime. The book addresses questions such as "What is meaning?", "What is truth?", "What are truth criteria in science?", "What is a theory?", "What is a model?" "What is a datum?", "What is information?", "What does it mean to understand something?", "What is space?", "What is time?", "How are these concepts articulated in science?" "What are values?" "What are the limits of science?", and many