George Campbell wrote The Philosophy of Rhetoric, a work, published in 1776, in which he attempts to synthesize Aristotelian rhetoric, Christianity, and natural science.  He discusses rhetoric in terms of an 18th century “faculty” psychology, a view in which different parts of the mind respond to arguments in different ways.  This chart may help explain the system:

In Campbell’s view, a persuasive speech moves through appeals to these four faculties, ending up by persuading the will to action.  One of the most interesting ideas in this work is Campbell’s rejection of syllogistic reasoning from probabilities in favor of a more scientific presentation of actual evidence.

Also in 1776, Campbell gave a sermon called “The Nature, Extent, and Importance of the Duty of Allegiance,” delivered at Aberdeen, December 12th, 1776. Campbell argues strongly against the American revolution and the Declaration of Independence specifically. Prior to the passage below, Campbell argues that it is almost never a good idea to overthrow established authority, which is established according to the will of God, and quotes extensively from the Bible in support. He also argues that there are lots of British subjects who pay taxes without having the right to vote for representatives, so why should the Americans complain?

In regard to the present quarrel, it may justly be said that it is the whole that is attacked. Indeed the ringleaders of the American revolt, the members of their congress, have, in their last declaration, pointed all their malice against the king, as tho’ in consequence of a settled plan, he had been adopting and pursuing tyrannical measures, in order to render himself absolute. They have accordingly spared no abuse, no insult by which they could inflame the minds of an unhappy and deluded people. Their expressions are such as decency forbids me to repeat. The means they employ are indeed of a colour with the end they pursue. But let those who can lay claim to any impartiality or candour, but reflect, and say in what single instance our benign sovereign has adopted any measure but by the advice of the British legislature, or pursued a separate interest from that of the British nation. It is solely concerning the supremacy of the parliament, the legislative body of Great Britain, and not concerning the prerogatives of the crown, that we are now contending. And ought not this circumstance to enhance our obligation to concur with alacrity as far as our influence will extend, in strengthening the hands of the government, now laid under a necessity of seeking by arms to bring back to their duty those insolent and rebellious subjects?

Later in the sermon he calls Americans who support the rebellion “our deluded fellow subjects on the other side of the Atlantic,” but he forgives them because “They are but the tools of a few ambitious, interested, and designing men, both on their side of the water and on ours.”  The whole sermon can be read here.  (I typed up this version from a scan of a copy of this pamphlet that was available in the U. C. Berkeley library.)

Campbell’s sermon provides an interesting context for a study of the rhetoric of the Declaration of Independence and its reception by the British public.