In his book, The Boston Painters, R. H. Ives Gammell makes the following statement:
“In short, a painter may properly be called an impressionist to just the extent that he renders aspects of nature as he saw them with unflinching honesty...”
On the surface that would seem to be a reasonably summary definition of an impressionist. Yet it leaves us with the question of whether any painter might be called "impressionist" who renders honestly this or that aspect of nature – something painters have always done. Thus he seems to suggest painters can be relatively impressionistic raising the implicit question as to whether there ought to be any such denomination. After all, all are impressionistic to one degree or another. He then goes on to say
“Given its most complete expression in the art of Velasquez, who is still its greatest exemplar, its (impressionism's) aim has ever been to convey on canvas the impression made on the painter by the subject he elects to depict.”
Gammell unintentionally leaves his readers potentially wondering about the very word “impression” itself, with its implied subjective interpretation when combined with the words, “made on the painter by the subject.”
On the first point Gammell is really following Monet, who says, “All great painters are more or less impressionists.” This somewhat defensive comment by Monet we can only take to mean that, of course, all of them tried to some degree to paint what they saw as it really appeared with relative degrees of success in achieving a truthfulness to nature.
However, when discussing where “impressionism was first fully made manifest [ie] in the work of ...Velasquez,“ his biographer, the painter/writer R. A. M. Stevenson, claims that his was a kind of painting based on recording not just some aspects for use in his pictures but whose modus operandi was to reproduce
“...a truth of general aspect. The whole effect of the canvas conveys a definite idea which has ordered every element of drawing, colour, and definition.... He wished any scene that he looked at in nature to be so treated in art as to express the quality and the distribution of the attention it had received from him in real life.”
... and not, to be clear, some subjective interpretation of it. Furthermore, quoting Stevenson,
“When you fail to grasp the ensemble of a Velasquez, when you miss its profound and touching truth, you can fall back on little else save a few disjointed facts of common realism. The art of the thing escapes you as the art of a Beethoven symphony escapes the man who only catches hold of occasional tag-ends of tunes hanging out of a preposterous and tangled coil of sound.”
Note the expression, “a few disjointed facts of common realism,” and try to grasp the essential difference between work that incorporates some truth and full-bodied, wholistic impressionism. Imagine, if you can, the inevitable differences in the practices required to attain what Gammell called their “mutually incompatible” goals. Velasquez's impressionism cannot be successfully made by the common strategies of academic painting but requires something considerably more like the subsequent and connected approach of the Boston School.