When Adams wrote in the Massachusetts constitution that “all men are by nature free and equal,” he meant morally all people were equal, though not physically:

“Common sense was sufficient to determine that it could not mean that all men were equal in fact, but in right, not all equally tall, strong, wise, handsome, active, but all equally men… The work of the same Artist, children in the same cases entitled to the same justice.”

– John Adams, by David McCullough