He was a son of Elizabeth "Eliza" Irwin Laughlin (1844–1929), and Duncan Clinch Phillips (1838–1917), a Pittsburgh window glass millionaire.
From the beginning Phillips conceived of his museum as "a memorial…a beneficent force in the community where I live—a joy-giving, life-enhancing influence, assisting people to see beautifully as true artists see."
With her assistance and advice, he developed his collection "as a museum of modern art and its sources," believing strongly in the continuum of artists influencing their successors through the centuries.
Phillips collected works by masters such as El Greco, calling him the "first impassioned expressionist"; Jean-Baptiste-Siméon Chardin because he was "the first modern painter"; Francisco Goya because he was "the stepping stone between the Old Masters and the Great Moderns like Cézanne"; and Édouard Manet, a "significant link in a chain which began with Goya and which [led] to Gauguin and Matisse.
Giving equal focus to American and European artists, Phillips juxtaposed works by Winslow Homer, Thomas Eakins, Maurice Prendergast, James Abbott McNeill Whistler, and Albert Pinkham Ryder with canvases by Pierre Bonnard, Peter Ilsted and Édouard Vuillard.
He exhibited watercolors by John Marin with paintings by Cézanne, and works by van Gogh with El Greco’s The Repentant St. Peter (circa 1600–05).
[4] Throughout his lifetime, Phillips had the prescience and courage to acquire paintings by many artists who were not fully recognized at the time, among them Marin, Georgia O'Keeffe, Arthur Dove, Nicolas de Staël,[5] Milton Avery and Augustus Vincent Tack.