Sanford Schwartz on Seymour Slive and this book:

“Hals provides something huge that we don’t get in Rembrandt or Vermeer and that complements them: a quicksilver and empathic responsiveness to people in all their variety. (…)

As Seymour Slive, our foremost authority on the artist, has suggested, Hals seems to have taken the key to each of his pictures from the nature of his encounter with the sitter. (Slive’s writings on Hals have the same warmth, directness, energy, and clarity that rise from the paintings.) The experience of the 1989 retrospective, which was largely Slive’s work and which can almost be recaptured in its catalog, where the reproductions are large and good, is that we are encountering a storehouse of subtle moods and expressions.

We see people who are, from painting to painting, alert, bemused, shy, in the middle of a remark, or mildly questioning. This one looks out at us appraisingly. One or two sitters feel like phonies or rakes, and we of course are drawn to them the most. Many are expressively neutral, but hardly one is inert. The cumulative effect of these many separate persons is that we know Hals himself. He is the generous, genial, and shrewd man, we tell ourselves, who has been able to capture them all.”
http://www.nybooks.com/articles/archives/2011/oct/13/quicksilver-frans-hals ( )