7. Now while considering the constitutional validity of a statute said to be violative of Article 14, it is necessary to bear in mind certain well established principles which have been evolved by the courts as rules of guidance in discharge of its constitutional function of judicial review. The first rule is that there is always a presumption in favour of the constitutionality of a statute and the burden is upon him who attacks it to show that there has been a clear transgression of the constitutional principles. This rule is based on the assumption, judicially recognised and accepted, that the legislature understands and correctly appreciates the needs of its own people, its laws are directed to problems made manifest by experience and its discrimination are based on adequate grounds. The presumption of constitutionality is indeed so strong that in order to sustain it, the Court may take into consideration matters of common knowledge, matters of common report, the history of the times and may assume every state of facts which can be conceived existing at the time of legislation.