I've really enjoyed reading the book Sparks ofGenius, which in describing a number of thinking tools in a dozen or so chapters, has the apt subtitle "schooling the imagination." I've posted previously about observation and emotion as the basis for discovery.
Abstraction in the book is described as the single defining feature of the idea or thing, arrived at by removing what's non-essential. The chapter provides many examples - love, honor, duty and justice are abstractions of complex and valued human qualities. Similarly, headlines, caricatures, initials and poetry are abstractions of longer, and perhaps less descriptive in their length, written works. Visually, Japanese stone gardens would be an abstraction of meditative Buddhism.
One of the greatest painters in history and a pioneer of abstraction was Pablo Picasso, who is quoted in the book as saying that "whatever is most abstract may perhaps be the summit of reality." Likewise, math is the physicist's reality tool. But in both cases abstraction is what is, approached differently, eliciting wonder.