The proletariat, which includes adjunct professors, has economic independence. It's free to sell its labor. Employers hire the labor by the hour, but confiscate the value created during each hour, including that over and above all the costs incurred. Everything created after the employee reaches the break-even point is surplus value. The fact that the employer helps himself to all the surplus value is what the word "exploitation" means in economic sociology.
I'd pretty much agree (and all my other posts on this thread clearly support the idea that adjuncts can be thought of as exploited labor), but traditional Marxist definitions of exploitation are tricky here, since in the vast majority of higher education, tuition doesn't begin to cover the costs of education. Very few colleges or universities are for-profit institutions, and schools really don't reach the break-even point in the classroom. (They can get grants, donations, interest from endowments, etc., but figuring out what kind of surplus value professors [tenured or adjunct] produce, or who the employers are who are helping themselves to this surplus value, is quite difficult.) There are, of course, lots of theorists who have modified Marxist theory in ways that make it more applicable to academia.
None of this changes the fact that if someone's exploited, they're still exploited even if they sign a second contract. . .
