Motivation or motive (from Medieval Latin motivus, from motus, past participle of movere "move") is the conscious or unconscious drive or need that incites a person to some action, inaction or behavior, providing incentive; often a goal or purpose. To motivate oneself or others, is to provide a motive for action or inaction. Both fear and devotion are powerful motivations. Sloth can also be a powerful motivation for avoiding responsibility and the possible pain or consequences of making any particular or general effort either for or against someone or something. Compare indifference.
"One of the theories that gives great insight on the first question - how to be sure we find happiness in our careers - is from Frederick Herzberg, who asserts that the powerful motivator in our lives isn’t money; it’s the opportunity to learn, grow in responsibilities, contribute to others, and be recognized for achievements." 
It's not what motivates a scientist's argument that determines its validity; it's the quality of the evidence and analysis that the scientist uses to support the argument.  See Hypothesis.
The scientists who contributed to the Manhattan project had the powerful motivation of ensuring that Adolf Hitler, then consolidating power over Europe and crushing the freedom of people there, would not get a super-weapon. (Discussions of Hiroshima and Nakagasaki tend to focus more on laments that 'innocent' civilians were killed, rather than on satisfaction that 'guilty' dictators were stopped; see Ethics of World War II.)
Religious people, motivation and dopamine levels in the brain
See also: Atheism and motivation and Atheism and the brain
According to Scientific American: "Research also suggests that a religious brain exhibits higher levels of dopamine, a hormone associated with increased attention and motivation." See also: Atheism and motivation and Atheism and the brain
- 5 science-backed ways to increase your motivation
- Motivation Is A Muscle: The 7 Best Ways To Substantially Increase Your Productivity, Forbes
- ↑ Derived from The Reader's Digest Great Encyclopedic Dictionary including Funk & Wagnalls Standard College Dictionary, 1966, The Reader's Digest Association, Inc. p. 884b-885a "motive".
- ↑ How will you measure your life?
- ↑ Stephen Meyer
- ↑ Ask the Brains, Scientific American, Dec 23, 2011