However, these considerations do not necessarily amount to conclusive disproof. Unknown leaf nodes have a proof and disproof number of unity. Disproof of a prediction is evidence of progress. He has funded a $1 million standing prize for its proof or disproof. For all nodes proof and disproof numbers are stored, and updated during the search. His studies of the distribution of quasars led to final disproof of steady state theory. Disproof of the traditional ideas of spontaneous generation is no longer controversial among biologists. The final disproof was shown by Claude R. Hitchcock and E. T. Bell. So this would be an example of disproof by begging the question.