Secant line a circle in the Euclidean plane, a line joining two of them would be a 2-secant (or "bisecant") and a line passing through only one of them would be a 1-secant (or "unisecant"). A unisecant in this example need not be a tangent line to the circle. This terminology is often used in incidence geometry and discrete geometry. For instance, the Sylvester–Gallai theorem of incidence geometry states that if points of Euclidean geometry are not collinear then there must exist a 2-secant of them. And the original orchard-planting problem of discrete geometry asks for a bound on the number of
What Is it Like to Be a Bat? only unquestionable fact of our experience", meaning that each individual only knows what it is like to be them (Subjectivism). Objectivity, requires an unbiased, non-subjective state of perception. For Nagel, the objective perspective is not feasible, because humans are limited to subjective experience. Nagel concludes with the contention that it would be wrong to assume that physicalism is incorrect, since that position is also imperfectly understood. Physicalism claims that states and events are physical, but those physical states and events are only imperfectly characterized. Nevertheless, he holds that physicalism cannot be understood without characterizing objective and subjective experience. That is