He meant something different than we mean. Aristotle noticed that despite having separate senses, we nonetheless end up with an integrated experience of the world, that all the data streams, in effect, are tied together.
When we look at a ball and hold it in our hands, we actually perceive its roundness through both sight and touch, but unless we stop to reflect, we usually don't notice that we have 2 grounds for thinking it's round. And if we lean forward and sniff the ball to discover how it smells, we don't usually have to "think" about where the smell is coming from - we "just know" it's the ball.
The modern meaning of common sense is sometimes described as "what everyone can agree about," but I don't think that can be right, since you often hear people say of academics: "they're smart but they lack common sense".
If academics can "lack common sense", then not everyone agrees can agree about it - just "sensible" people agree.
I wonder if the meaning is in fact related to Aristotle's meaning. I wonder if by "common sense" we now mean "judgments that clearly tie back to perception", as opposed to judgments that look like flights of fancy.
Rand didn't always like the way other people used the term, but she often used it herself with a positive meaning. She gave 2 different explanations of what it was:
That which today is called "common sense" is the remnant of an Aristotelian influence, and that was the businessman's only form of philosophy. ("For the New Intellectual", 1961)
Americans are the most reality-oriented people on earth. Their outstanding characteristic is the childhood form of reasoning: common sense. It is their only protection. But common sense is not enough where theoretical knowledge is required: it can make simple, concrete-bound connections—it cannot integrate complex issues, or deal with wide abstractions, or forecast the future. ("Don't Let It Go", 1971)There may be a way to tie these 2 passing comments into one theory.
But, at the moment, that leaves me feeling leery.