This article is devoted to define and characterize ‘Science’ as a discipline by the fundamental principles of scientific investigation. In particular, we propose and argue that ‘Science’ be defined by a set of principles / criteria which underlies scientific- investigation. We argue that this set must include the following principles: (1) Rationality, (2) Objectivity (3) Universality, (4) Internal Consistency, (5) Uniqueness, (6) Reproducibility, (7) The Principle of Falsification, (8) Simplicity and Elegance and (9) Experimental Observation and Verification. We elaborate, through illustrative examples, the justification of the above set of criteria. `Scientific temper’ essentially means the cultivation of these principles, as attitudes / value-system adopted as “ways of life”. We discuss the relevance of the inculcation of scientific temper in the modern context. Finally, the scope and limitations of the scientific method are highlighted and an attempt is made to dispel several misconceptions and myths associated with Science and scientists.