As a philosophy professor, one of my central goals is to teach students to think critically. However, one difficulty with determining whether critical thinking can be taught, or even measured, is that there is widespread disagreement over what critical thinking actually is. Here, I reflect on several conceptions of critical thinking, subjecting them to critical scrutiny. I also distinguish critical thinking from other forms of mental processes with which it is often conflated. Next, I present my own conception of critical thinking, wherein it fundamentally consists in acquiring, developing, and exercising the ability to grasp inferential connections holding between statements. Finally, given this account of critical thinking, and given recent studies in cognitive science, I suggest the most effective means for teaching students to think critically.