I'm in an intro history class, US history up to 1877, and the textbook assigned/used is A People & A Nation A History of the United States 11th edition volume 1, by Kamensky, Sheriff, Blight, Chudacoff, Logevall, Bailey, and Norton, published by Cengage, ISBN 978-1-337-40272-9. Anyways, Just wanted to get that out of the door to avoid any mistakes. The textbook in Chapter 7, on page 183 in reference to the 3/5ths compromise that, "(The formula reflected delegate's judgement that slaves were less efficient producers of wealth than free people, not that they were three-fifths human and two-fifths property.)" This is the first time I've heard that claim. When I asked my professor where that claim came from, because I had never heard it before, he didn't seem to know either. I couldn't find any citation or source within the textbook. My professor suggested this may be a newer claim supported by more recent work/authorship on some previously overlooked or undiscovered source, but I'm pretty lost. How legitimate is this assertion?
The formula reflected delegate's judgement that slaves were less efficient producers of wealth than free people, not that they were three-fifths human and two-fifths property.
I'd recommend checking out Federalist number 54 which is James Madison's letter to the people of New York where he justifies the 3/5ths compromise specifically.
Federalist 54 includes phrases such as:
The federal Constitution, therefore, decides with great propriety on the case of our slaves, when it views them in the mixed character of persons and of property. This is in fact their true character.
as well as
In every State, a certain proportion of inhabitants are deprived of this right by the constitution of the State, who will be included in the census by which the federal Constitution apportions the representatives. In this point of view the Southern States might retort the complaint, by insisting that the principle laid down by the convention required that no regard should be had to the policy of particular States towards their own inhabitants; and consequently, that the slaves, as inhabitants, should have been admitted into the census according to their full number, in like manner with other inhabitants, who, by the policy of other States, are not admitted to all the rights of citizens. A rigorous adherence, however, to this principle, is waived by those who would be gainers by it. All that they ask is that equal moderation be shown on the other side. Let the case of the slaves be considered, as it is in truth, a peculiar one. Let the compromising expedient of the Constitution be mutually adopted, which regards them as inhabitants, but as debased by servitude below the equal level of free inhabitants, which regards the SLAVE as divested of two fifths of the MAN.
emphasis mine.
You can look through the letter, and see that James Madison does not mention wealth production or taxation anywhere in his letter to the people of New York.
That is fairly strong evidence that at least two framers (Madison as author, Hamilton as editor of Federalist Papers) were comfortable publishing the idea that enslaved people were 3/5 human, 2/5 property.
You might be interested in what /u/sowser wrote to answer the question In colonial America , why was 3/5 chosen as the value of a slave when counting population?, with more sources for you and the professor to read.
/u/freedmenspatrol and /u/FatherAzerun might have an opinion too.
EDIT: Fixed the link.