You could say that he appealed to pathos. It's an appeal to emotion while ethos is to credibility. He used pathos to speak about sad things like secession and about the evils of slavery and why it should end. He didn't have to appeal to credibility because he was already the president so everyone knew why he was competent.
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Economic and political factors, the U.S. was influenced to practice imperialism, particularly during the late 19th and early 20th centuries.
