ve a reasonable tendency to promote the general welfare and must not
arbitrarily invade the rights of particular persons or classes. Inasmuch
as the hard and fast rules of an age when conditions of life were
simpler are no longer practicable under the more complex relationships
of modern times, there is today an inevitable tendency to force these
rules to greater flexibility. *

* Notwithstanding what is said above, it is also true that the
modern doctrine of "the police power" owes something to Marshall's
interpretation of the "necessary and proper" clause in M'Culloch
vs. Maryland, which is frequently offered nowadays as stating the
authoritative definition of "a fair legislative discretion" in relation
to private rights. Indeed this ingenious transposition was first
suggested in Marshall's day. See Cowen (N. Y.), 585. But it never
received his sanction and does not represent his point of view.

And this difference in the point of view of the judiciary connotes a
general difference of outlook which makes itself felt today even in
that field where Marshall wrought most enduringly. The Constitution was
established under the sway of the idea of the balance of power, and with
the purpose of effecting a compromise among a variety of more or less
antagonistic interests, some of which were identified with the cause
of local autonomy, others of which coalesced with the cause of National
Supremacy. The Nation and the States were regarded as competitive
forces, and a condition of tension between them was thought to be not
only normal but desirable. The modern point of view is very different.
Local differences have to a great extent disappeared, and that general
interest which is the same for all the States is an ever deepening one.
The idea of the competition of the States with the Nation is yielding
to that of their cooperation in public service. And it is much the same
with the relation of the three departments of Government. The notion
that they have antagonistic interests to guard is giving way to the
perception of a general interest guarded by all according to their
several faculties. In brief, whereas it was the original effort of
the Constitution to preserve a somewhat complex set of values by nice
differentiations of power, the present tendency, born of a surer vision
of a single national welfare, is toward the participation of all powers
in a joint effort for a common end.

But though Marshall's work has been su