...it's true; but what kind of a long novel would it be if thehero had no incentive... 
Various 「Astounding Stories, August, 1931」
...The incentive to this step was the inhuman treatment he was subjected to...
William Still 「The Underground Railroad」
...He gave the black bull ashrewd glance out of his little cunning eyes, and paid no furtherattention; and the bull, seeing no incentive to a quarrel, snorteddoubtfully and lay down again...
Charles G. D. Roberts 「The Watchers of the Trails」
...Hugo set down my bag, accepted another gold coin; and with a queersidelong smile, the incentive for which I had not the slightest idea,he vanished...
Various 「Astounding Stories of Super-Science September 1930」
...In their relation, he gave everything in the way of incentive andinitiative, and she returned her entire effort loyally...
Edward Singleton Holden 「Sir William Herschel: His Life and Works」
...The problem as thus presented was one of the most difficult we canperceive of, but the difficulty was only an incentive to attacking itwith all the greater energy...
Simon Newcomb 「Side-lights on Astronomy and Kindred Fields of Popular Science」
...This is a higher, nobler,and greater incentive to righteousness than any life of personal rewardor fear of punishment in a future life...
Dr. D.M. Brooks 「The Necessity of Atheism」
...Dancing not only proves an incentive, butoffers an opportunity in its intervals...
Watkin Tench 「A Complete Account of the Settlement at Port Jackson」
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