In writing about America, Lord Bryce once described public
opinion as "omnipotent yet indeterminate, a sovereign to whose
voice every one listens, yet whose words, because he speaks with
as many tongues as the waves of a boisterous sea, it is so hard to
catch." Today we might not so flatly ascribe omnipotence to the
popular mind; yet the elusive thing that Bryce chose as the secret
key to American politics remains, for students of a democratic
society, perhaps the most basic and surely the most baffling of
problems. If we indeed live under the sway of public opinion, we
have an urgent responsibility to understand its forms, its function-
ing, and its flux.

In America public opinion acts like a monetary system that is
highly respected in spite of the curious fact that everybody may
mint the currency and no one knows exactly what it is worth.
Public opinion, in other words, is not an autonomous power but
a medium of exchange. It circulates more or less freely; it gives
force to our values; it registers an intricate contention of interests
and desires; men lust for control of it; and periodically it under-
goes an astonishing inflation. Consequently its history provides an
unusually comprehensive approach to many aspects of our national
development. Within the medium of public opinion changes in
events, institutions and ideas meet and blend in a single historical
process.

I have examined one of the important themes in the recent
American past in these terms. Although I began with simpler in-
tentions, this book has grown well beyond its original design. At
first I intended only to trace popular attitudes on immigration re-
striction. But I discovered that I was dealing with elements that
could scarcely be defined--far less understood--within the limits
of a functional context as simple as a legislative program. As a re-
sult, this book attempts a general history of the anti-foreign spirit
that I have defined as nativism. It tries to show how American

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