"The chief requirement of this phenomenon is the appearance of a number of books or art within a brief time. The shorter the span in which they are bunched, the more valid the concentration is."
Another agitation is the Creative Concentration, a date surrounded by a concentration of great works of art. A Creative Concentration can include books, paintings, controversial plays, and music including symphonies and operas. Creative Concentrations always move from easy to difficult. Another feature of a creative concentration is that the merit of the books is recognized abroad as at home. Influence is what counts, not worth. Not every agitation is followed by repercussions at all three intervals. Some counts are more important than others. To estimate which, correlate the intervals of one country with those of its rivals. When ease and difficulty are scheduled for the same time (when two opposing intervals expire at the same time), it is unknown which will take effect first. Expect rapid shifts in fortune. Remember; disasters are momentary while stretches of prosperity last longer.
Lindsay gives the Enlightenment as a prime example of a Creative Concentration and dates it to 1749 based on a number of books which appeared around that year. Forty years later, a difficulty would be expected for France and, indeed, 1789 was the year of the French Revolution.
Einstein's Annus Mirabilis papers, "a seminal exposition of a new principle in physics," published in 1905, together with a host of other German writers, formed a concentration that year. Forty years later marked the defeat of Germany in World War II.
"The technical historian is not afraid of coupling ideas from unrelated categories. He does not reject continuity of thought, but the connection need not be the obvious one that seems appropriate to the sentient mind. The meaningful thought is that which has been transformed, and perhaps rechanneled, through a period of subconscious rumination. It becomes an ingrained attitude rather than a directed effort."