[2] Berenson was a major figure in the attribution of Old Masters, at a time when these were attracting new interest by American collectors, and his judgments were widely respected in the art world.

After his home and lumber business were destroyed by fire, he lived with his more traditionalist in-laws who pressured him to enroll Bernard with a Hebrew and Aramaic tutor.

Among his friends were American writer Ray Bradbury, who wrote about their friendship in The Wall Street Journal and in his book of essays, Yestermorrow; Natalie Barney, who lived in Florence during World War II, and also her partner, Romaine Brooks; and art collector Edward Perry Warren.

[9] His circle of friends also included Isabella Stewart Gardner, Ralph Adams Cram, and George Santayana, the latter two having met each other through Bernard.

Early in his career, Berenson developed his own unique method of connoisseurship by combining the comparative examination techniques of Giovanni Morelli with the aesthetic idea put forth by John Addington Symonds that something of an artist's personality could be detected through his works of art.

"[13] ) Starting with his The Venetian Painters of the Renaissance with an Index to their Works (1894), his mix of connoisseurship and systematic approach proved successful.

It was quickly followed by The Florentine Painters of the Renaissance (1896), lauded by William James for its innovative application of "elementary psychological categories to the interpretation of higher art".

[citation needed] In 1897, Berenson added another work to his series of guides, publishing The Central Italian Painters of the Renaissance.

A portrait of daily life at the Berenson "court" at I Tatti during the 1920s, may be found in Sir Kenneth Clark's 1974 memoir, Another Part of the Wood.

[citation needed] In 1923, Berenson was called to give expert witness in a famous case brought by a Mrs. Andrée Hahn of Kansas City against Duveen.

In 1920, Hahn wanted to sell a painting that she believed to be a version of Leonardo's La belle ferronnière and whose authorship is still debated.

At the trial in New York in 1929, where the expert witnesses did not appear, the jury was not convinced by Berenson's Paris testimony, in part because, while under cross-examination there, he had been unable to recall the medium upon which the picture was painted.

It was also revealed that Berenson, as well as other experts who had testified in Paris, such as Roger Fry and Sir Charles Holmes, had previously provided paid expertise to Duveen.

Recent scholarship has established that Berenson's secret agreements with Duveen resulted in substantial profits to himself, as much as 25% of the proceeds, making him a wealthy man.

The Letters of Bernard Berenson and Isabella Stewart Gardner, 1887-1924, edited by Rollin van N. Hadley, was published by Northwestern University Press in 1987.