Ralph Waldo Emerson (1806-1882) was an American poet, essayist and lecturer. He led the Transcendentalist movement of the 1800s, which believed in the power of the individual, and gave over 1,500 lectures, publishing dozens of essays and poems throughout his life.
"The ancestor of every action is a thought." is a quote from the essay "Spiritual Laws" published in Essays: First Series (1841). Emerson's collections of essays originally began as a series of lectures Emerson gave in and around Boston. These lectures, and later essays, outline and also elaborate on some of the fundamental principles of Transcendentalism.
Though "Spiritual Laws" is not Emerson's most well know work, nor is it considered his most well written, it does delve into and develop some of Emerson's most well know philosophical concepts, such as self-reliance and individualism.
Emerson says, "We know that the ancestor of every action is a thought." to make a case there is a time for action, and a time for thought, that action is not inherently superior to thinking, and neither is thinking inherently superior to action.
Two paragraphs before this particular quote Emerson writes:
"Nor can you, if I am true, excite me to the least uneasiness by saying, `He acted, and thou sittest still.' I see action to be good, when the need is, and sitting still to be also good… Heaven is large, and affords space for all modes of love and fortitude. Why should we be busybodies and superserviceable? Action and inaction are alike to the true."
Emerson made the case that some people are called to action, some to thought, and some to both. If the individual is true to themselves and does not rely on outside entities for their identity, then the individual will do what they are called to do, and respect every other individual doing the same.
Emerson goes on to make the case that we should not look busy for the sake of looking busy, the rich mind needs nothing, but "lies in the sun and sleeps, and is Nature. To think is to act."
"The ancestor of every action is a thought." - Emerson