McKinley believed that Filipinos were ignorant and childlike, and that they were unfit for self-government. He framed US policy in Philippines as a humanitarian mission, designed to bring the alleged benefits of Western civilization to the Filipino people. Rudyard Kipling's famous poem "White Man's Burden" was written to encourage US annexation of the archipelago as a duty that attended being a powerful nation. Social Darwinistic assumptions about western superiority played a major role, as US policy became a mixture of altruism and selfishness. In the end, most humanitarian arguments for imperialism in the Philippines were a justification for national interest, both economic and military. Ultimately, the Philippines were viewed as a way to extend US influence into South Asia and especially the much-coveted markets in China.
President McKinley personally debated the question of what to do with the Philippines for a long time. McKinley was a very religious man, and his religious beliefs played a big role in his decision to retain the islands instead of giving them autonomy. In a speech to the General Missionary committee of the Methodist-Episcopal Church, he explained his reasoning.
“I don't know how it was, but it came: (1) That we could not give them back to Spain - that would be cowardly and dishonorable; (2) that we could not turn them over to France or Germany - our commercial rivals in the Orient - that would be bad business and discreditable; (3) that we could not leave them to themselves - they were unfit for self-government - and they would soon have anarchy and misrule over there worse than Spain's was; and (4) that there was nothing left for us to do but to take them all, and to educate the Filipinos, and uplift and civilize and Christianize them, and by God's grace do the very best we could by them, as our fellow men for whom Christ also died.”
The above quote shows his reasoning very clearly. He didn’t want to return them to Spain, because it would be a significant show of weakness and it made no sense to return such a valuable strategic acquisition. Not taking possession would open them up to German or French influence, losing the U.S. a valuable market for their goods. McKinley did not believe that the Philippines were capable of governing themselves, an excuse with a certain amount of racism in it. Finally, McKinley saw it as an opportunity to bring western civilization to the islands, a White Man’s Burden argument that was very popular at the time as an excuse for imperialism.