As early as 1880, James had contributed an article in French to the periodical "La Critique philosophique", of Renouvier and Pillon, entitled "Le Sentiment de l'Effort". Four years later, a couple of articles by him appeared in the journal "Mind": "What is an Emotion?" and "On some Omissions of Introspective Psychology". Bergson quoted the first two of these articles in his 1889 work, "Time and Free Will". In the following years, 1890–91 appeared the two volumes of James's monumental work, "The Principles of Psychology", in which he refers to a pathological phenomenon observed by Bergson. Some writers, taking merely these dates into consideration and overlooking the fact that James's investigations had been proceeding since 1870 (registered from time to time by various articles which culminated in "The Principles"), have mistakenly dated Bergson's ideas as earlier than James's.