“Pennsylvania and Massachusetts passed laws to end slavery in their states in 1780… before the revolution was over, 9 years before the Constitution went into effect, and over 50 years before the British outlawed it.”
Of the 13 original slave states, 13 of them voted to enshrine slavery into the United States Constitution in 1787. This includes Pennsylvania and Massachusetts.
In fairness, probably the only reason Pennsylvania and Massachusetts went along with giving slavery legal status in the Constitution was because it was in their own economic and political best self interest.
No, you are wrong on that. The reason they allowed slavery in the Constitution was in order to have unanimous consent to the document. They knew that at the very least South Carolina and Georgia would not have consented to the constitution with out slavery, and even Georgia may have gone along because of their concern for the British in Florida being a threat.
You had strong opponents of slavery such as Franklin in Pennsylvania who actually were involved in drafting the constitution. They did not go along for economic reasons. They saw it as necessary in order to stay United. They also saw slavery as a poor economic system which would end on its own soon enough. And it would have if not for the invention of the cotton gin, short fiber cotton and the growth of king cotton in the early decades of the 19th century. That, they could not have predicted.
No. Rhode Island was not even present(represented) at the 1787 Convention being the troublemaker it had always been at that time, but even excluding this technicality that there were only 12 still no.
They voted to enshrine non-slavery into the United States Constitution in 1787.
Any CTRL + F can quickly return exactly zero results on the actual text of the Constitution. This is a simple textualist task in our modern era of word browsers and advanced web browsers. The words slave or slavery are simply not there. The words were explicitly removed by the abolitionists and rightly so. And they stated the very simple reason why the word could not be included.
It was believed to be wrong "to admit in the Constitution the idea that there could be property in men." August 25th, 1787. That's the day.
https://avalon.law.yale.edu/18th_century/debates_825.asp
And so, the idea that there can be a property in men, is not admitted as a constitutional truth. Excluding the word is not conclusive of enshrining slavery. And yes, the Founders were very exacting in making sure they tried their best to put words in place. They didn't make a mistake on this one, one way or the other. A group of Founders didn't slip, fall over, and trip then and look up and realize oh my gosh I forgot to include the word slave!
No.
Conclusive of enshrining slavery would be that the word is used multiple times in the Constitution. At "best" what they did was look the other way knowing that the only way union was going to work was through toleration and activism for abolitionism on a state-by-state basis. This was also explicitly referenced at the Convention.