These have been the two great poles of the religious life in both the Western and Eastern traditions.
On the one hand, there is the "call" to take the message of revelation to the world, by selfless service to humanity, by proselytization, or by violent crusade. Thus we have mission sisters courageously serving ebola patients in equatorial Africa, evangelicals knocking on doors with religious tracts in hand, and Taliban jihadists forcibly imposing their God-given regimen on an often unwilling population.
At the other extreme is retreat into self in search of the essential gnosis of revelation. This tendency gave rise to the monastic movements of West and East -- the spirituality of Thomas Merton and the Zen scholar D. T. Suzuki, for example -- visible to us in its most extreme form in the lives of Desert Fathers such as Antony and Jerome.
To a certain extent, I suppose, a predisposition to activism or introspection is innate in each of us, and religion is just one of the givens which our natural talents serve. Thoreau needed no holy book to take him to the seclusion of Walden Pond, and one suspects that Martin Luther King would have been a political activist on behalf of his people with or without religious motivation.
Science is by definition a public activity, although it has its share of hermits. Darwin was loath to leave his "desert cave" at Down House in Kent, and let his more activist friends carry his scientific ideas into the public forum. Huxley loved engagement as much as Darwin loved his solitude.
The religious naturalist, among whom we might count Darwin and perhaps even Merton, needs no divine revelation to adopt a life of either quiet reflection or social activism. What distinguishes the religious naturalist from others who call themselves religious is the absence of dogma, which means that retreat is generally into the silent contemplation of nature, and activism takes the form of service without proselytization.