Such a construction would beget endless uncertainty and embarrassment. The cases must be palpable and extreme in which it could be pronounced with certainty that a measure was absolutely necessary, or one without which a given power would be nugatory. There are few measures of any government which would stand so severe a test. To insist upon it would be to make the criterion of the exercise of an implied power _a case of extreme necessity_; which is rather a rule to justify the overleaping the bounds of constitutional authority than to govern the ordinary exercise of it. The degree in which a measure is necessary can never be a test of the legal right to adopt it. The relation between the _measure_ and the _end_; between the nature of the _mean_ employed towards the execution of a power, and the object of that power must be the criterion of constitutionality, not the more or less _necessity_ or _utility_. The means by which national exigencies are to be provided for, national inconveniences obviated, and national prosperity promoted, are of such infinite variety, extent, and complexity, that here must of necessity be great latitude of discretion in the selection and application of those means. Hence the necessity and propriety of exercising the authority intrusted to a government on principles of liberal construction. While on the one hand, the restrictive interpretation of the word _necessary_ is deemed inadmissible, it will not be contended on the other, that the clause in question gives any new and independent power. But it gives an explicit sanction to the doctrine of implied powers, and is equivalent to an admission of the proposition that the government, _as to its specified powers and objects_, has plenary and sovereign authority.