"To bring the school to a different level of excellence, we had to replace about 40 substitute professors," Dr. Lirtzman said.
Cornelia has also been an adjunct professor, a substitute teacher, a church youth director, and a faculty advisor for a college student publication.
So I negotiated with my professors to substitute a thesis-length report on those events.
"A great deal would have to change for The Journal to appeal to the average Times reader as a substitute," said Tunku Varadarajan, a business professor at New York University who writes for The Daily Beast blog and is a former assistant managing editor of The Journal.
The risks are greater for lesser colleges, which may be tempted to drop some of their own introductory courses — and some professors who teach them — and substitute cheaper online instruction from big-name professors.
It is not completely clear whether craft beer and mass-produced beer are complements or substitutes, said Patrick Emerson, an economics professor at Oregon State University and beer enthusiast.
"What they want is to substitute technology for teachers," said Alex Molnar, professor of education policy at Arizona State University.
This week MSNBC executives expressed unreserved enthusiasm about another substitute for Ms. Maddow, Melissa Harris-Perry, a professor of political science at Tulane University, who filled in for the first time last week.
It will be up to the Justice Department and Federal Communications Commission to determine whether given these market realities, existing competitors offer services that are reasonable substitutes, said Herbert Hovenkamp, an antitrust law professor at the University of Iowa.
"They deployed an inadequate force as a politically palatable substitute for doing nothing," said Paul F. Diehl, a professor of political science at the University of Illinois at Urbana-Champaign.
