"Some of these ideas, I have ... already expressed publicly in a series of lectures delivered at Columbia university between the autumn of 1915 and th...
"Some of these ideas, I have ... already expressed publicly in a series of lectures delivered at Columbia university between the autumn of 1915 and the spring of 1917, and in newspaper articles published during the same period in Sunday editions of the New York times, the New York sun, and the Morning telegraph."--Foreword.