"Negatively Defined" Objects: Summarize the Best Observational Evidence That Astronomers

"Negatively Defined" Objects: Summarize the best observational evidence that astronomers have for the existence of stellar mass black holes. Contrast this with the observational evidence that pulsars exist. Do you agree or disagree with the statement that the best evidence we have for stellar mass black holes is that we have detected objects for which an alternate explanation is lacking? How does your answer influence your confidence in the existence of black holes? Does the strong observational confirmation of Einstein's general theory of relativity (see Special Topic General Relativity and Spacetime in Section 13.3) increase your confidence in the existence of black holes? Should it?