Question: Contrary to what he is best known for, what did Van Gogh consider his greatest ambition?
About the article "Vincent van Gogh", section "Portraits".

Candidate passages:
Van Gogh, known for his landscapes, seemed to find painting portraits his greatest ambition.
To his sister he wrote, "I should like to paint portraits which appear after a century to people living then as apparitions.
By which I mean that I do not endeavor to achieve this through photographic resemblance, but my means of our impassioned emotions -- that is to say using our knowledge and our modern taste for color as a means of arriving at the expression and the intensification of the character.
"While Van Gogh had few opportunities to make portraits, he completed at least three at Saint-Rémy. 
Van Gogh, known for his landscapes, seemed to find painting portraits his greatest ambition.
He said of portrait studies, "the only thing in painting that excites me to the depths of my soul, and which makes me feel the infinite more than anything else."
Van Gogh wrote further of the meaning he wished to evoke: "in a picture I want to say something comforting as music is comforting.
I want to paint men and women with that something of the eternal which the halo used to symbolize, and which we seek to communicate by the actual radiance and vibration of our coloring.
"As much as Van Gogh liked to paint portraits of people, there were few opportunities for him to pay or arrange for models for his work.
He found a bounty in the work of the Roulin family, for which he made several images of each person.
In exchange, Van Gogh gave the Roulin's one painting for each family member.
As the Roulin family was similar in size to Van Gogh's own, in his psychological approach Lubin suggested that Van Gogh may have adopted them as a substitute. 
Van Gogh, known for his landscapes, seemed to find painting portraits his greatest ambition.
He said of portrait studies, "the only thing in painting that excites me to the depths of my soul, and which makes me feel the infinite more than anything else."
To his sister he wrote, "I should like to paint portraits which appear after a century to people living then as apparitions.
By which I mean that I do not endeavor to achieve this through photographic resemblance, but my means of our impassioned emotions -- that is to say using our knowledge and our modern taste for color as a means of arriving at the expression and the intensification of the character.
"As much as Van Gogh liked to paint portraits of people, there were few opportunities for him to pay or arrange for models for his work which may have been another factor in his desire to make a portrait of his mother. 
List of works by Vincent van Gogh is an incomplete list of paintings and other works by the Dutch artist Vincent van Gogh (1853–1890).
Little appreciated during his lifetime, his fame grew in the years after his death.
According to the legend van Gogh sold only one painting, "The Red Vineyard", bought for 400 Francs by the painter and art collector Anna Boch.
Today, he is widely regarded as one of history's greatest painters and an important contributor to the foundations of modern art.
Van Gogh did not begin painting until his late twenties, and most of his best-known works were produced during his final two years.
He produced more than 2,000 artworks, consisting of around 900 paintings and 1,100 drawings and sketches.
In 2013 "Sunset at Montmajour" became the first full-sized Van Gogh painting to be newly confirmed since 1928.
Today, many of his pieces—including his numerous self portraits, landscapes, portraits and sunflowers—are among the world's most recognizable and expensive works of art.
On March 30, 1987, "Irises" was sold for a record US$53.9 million at Sotheby's; on May 15, 1990, his "Portrait of Dr. Gachet" was sold for US$82.5 million at Christie's, establishing a new price record until exceeded in 2004 by a Picasso painting.
The Van Gogh Museum in Amsterdam is dedicated to Van Gogh's work and that of his contemporaries.
The Kröller-Müller Museum in Otterlo (also in the Netherlands), has another considerable collection of his paintings.
The listing is ordered by year and then by catalogue number.
All works listed here are oil on canvas unless otherwise indicated.† Denotes paintings which are recent recordholders for the highest price paid for a painting at an auction: see list of most expensive paintings. 
Although Van Gogh is best known for his landscapes, he seemed to find painting portraits his greatest ambition.
He said of portrait studies, "The only thing in painting that excites me to the depths of my soul, and which makes me feel the infinite more than anything else.
"To his sister he wrote, "I should like to paint portraits which appear after a century to people living then as apparitions.
By which I mean that I do not endeavor to achieve this through photographic resemblance, but my means of our impassioned emotions – that is to say using our knowledge and our modern taste for color as a means of arriving at the expression and the intensification of the character.
"Of painting portraits, Van Gogh wrote: "in a picture I want to say something comforting as music is comforting.
I want to paint men and women with that something of the eternal which the halo used to symbolize, and which we seek to communicate by the actual radiance and vibration of our coloring."