I will only consider the first publication "Thoughts and Sentiments on the Evil and Wicked Traffic of the Slavery and Commerce of the Human Species" 1787 in this Penguin Classic.
This pamphlet is essential because it comes from an African man who was deported at the age of 13 into slavery in the West Indies and then had the great luck of being bought out of it by some English gentleman who made him his servant, provided him with education and introduced him to the Christian religion. We can see from this simple situation that the man is a privileged witness and yet at the same time has enough distance to be objective, I mean to move beyond simple resentment to reach compassion and, as we would say today, empathy.
I will not reside on the testimony itself for a simple reason: the author does not really testify on what the Black Africans have been forced to submit to in slavery. Apart from the high death toll of this position when captured, when transported and when seasoned, and then the similarly high death toll of slavery afterwards, the pamphlet is absolutely vague and shy about the detailed brutality of this situation. Apart from a couple of whippings that are discreetly mentioned, the only case that stands out is a trial in London in 1783. The captain and shipping company of a slave ship were sued by the insurance company that refused to pay compensation for the slaves they willingly threw overboard so that the sickness that was raging on the ship could not be invoked as the cause of the loss of the slaves. If sickness had been the cause the insurance company would have been justified not to pay compensation. But if the slaves were lost at sea by drowning then the company could claim damages from the insurance company. But the insurance company, due to a testimony from a member of the crew considered that the wilful decision to drown the slaves could in no way be considered as a sailing hazard and hence could not qualify for compensation. The courts though followed the shipping company and ordered the insurance company to pay £3,960 representing £30 per drowned slave, which is an important amount of money. The insurance company appealed but there is no record of the final decision. And I must say, Cugoano does not give these details. The editor's notes to the pamphlet provide a lot of detail on what amounts to allusions in Cugoano's pamphlet.
Now, in 1787 the case of the equality of all humans, no matter what their genetic particulars may be was for sure not advanced at all. The only seemingly scientific approach is Montesquieu's climate theory which is alluded to once without the name of his author. Newton is mentioned but his reference is only ethical.
The basic corpus of arguments is an extremely long list of verses from the Bible, Old Testament as well as New testament. Today these arguments are slightly outmoded if not counter-efficient. The case of Cain being marked by God to protect him against those who would like to kill him for his killing Abel, a case that is still referred to by Mormons, probably not all of them, but definitely some, is absurd since Cain leaves the Levant to go north, hence the blacks should be in Europe not in Africa, though the blacks are clearly identified as Ethiopians in the Bible. This is not used by Cugoano who develops in length the fact that God's mark was a protection. Then since all descendants of Cain are destroyed by the flood, so does Cugoano asserts, the next stage is the case of Canaan, the grand son of Noah who sees the nudity of his grandfather with his own father present who sees that nudity too. Canaan is condemned in his descendants to be the servants of the servants of the other brother's descendants. Servants of servants could mean lower than servants and Cugoalno harps on the curse and its justified nature and the total absence of protection which implies along series of destructive wars against them from the Israelites, events on which Cugoalno spends a lot of writing space.
All that will sound foolish today, but in the 18th century that was all they had to work on. The Declaration of Independence of 1776 was doing just the same: the equality of all men was stated as the result of God's creation. We can note though that Blacks, Indians, women, non-free men and males under 21 were not considered as eligible for citizenship. That's a lot of inequality at the time, even if things have changed tremendously in the meantime, though the words have not and are just interpreted in a different way.
It would be interesting to pick all the biblical quotations and show how Cugoano uses them to support his case and very often shifts the meaning from the biblical context to his own discourse. But that would be of little interest except to prove that these biblical texts can be interpreted in many different ways and that those who are basic segregationists use the Bible to justify their position, though things having changed slightly their segregationist attitude is discreet on the question of "races" or even "sexes" but has become open on the question of "sexual orientation". The best example of this hypocritical use of the Bible is the Mormons as a whole, as a church or as a US presidential candidate in 2012.
This book then has one main interest and it is ONLY historical: it shows how the anti-slavery people in the 18th century were reduced to either biblical quotations like Cugoano, or philosophical humanistic assertions like Diderot, Rousseau or some others. It's only in the 19th century that science was going to start, and only start, getting biological, anthropological and physical elements, though the concept of "primitive man" will survive up to Lévy Bruhl and Paul Radin, and some others in the second half of the 20th century. At the same time another ideology is developing that mixes up the various cultures or civilizations of humanity and pretend that there is only one universal civilization and even at times pretend they do not see any basic differences among cultures. This is common with people who decide that religion is not to be taken into account due to their absolute and fundamentalist secularism. This extreme secularism is too often the blind response to the blinding reverse ideology that pretends there is a hierarchy of civilizations and cultures among human groups, turning the phylogenic scientific method of anthropology and linguistics into a moralistic and segregationist elimination of those that are not in agreement with the model these censors have in mind, which is of course themselves and their own culture and civilization (both being in the singular) that they declare universal.
Cugoano can maybe bring some people in that field to some modesty and realistic reflection.
Dr Jacques COULARDEAU