No doubt, one of the most significant philosophical systems in the west which is said to be a turning point in developing the western thought is that of the distinguished German philosopher, Immanuel Kant (1724-1804). In the first section of 'the Critique of Pure Reason', Kant is concerned with the three human faculties: sensation, understanding, and reason. In Transcendental Dialectic which is considered to be the most important part of his 'Critique', Kant seeks to study reason, ideas and their relation with sensation and understanding. According to Kant, reason may have two distinct functions: logical and pure (transcendental) functions. Reason is of certain principles through which rules of understanding can be united. These principles are what we call apriori universal knowledge which are derived from the concepts of pure reason. Reason, for Kant, has another function according to which it is of a fundamental principle, a transcendental principle. This fundemental principle is based on the proposition that the chain of logical premises to which reason gain access, is of unconditioned or Absolute, reason arrives at concepts (ideas) which has no exemplifications in our experience. These concepts are what Kant calls the "ideas of pure reason". These pure ideas or concepts have positive functions which are regulative and have some negative functions which are constitutive. These two functions are explained in detail throughtout the article.