Chacholski, WojciechScherer, JeromeWerndli, Kay2017-03-272017-03-272017-03-27201610.5802/aif.3074https://infoscience.epfl.ch/handle/20.500.14299/136032WOS:000393926200013Consider a push-out diagram of spaces C <- A -> B, construct the homotopy push-out, and then the homotopy pull-back of the diagram one gets by forgetting the initial object A. We compare the difference between A and this homotopy pull-back. This difference is measured in terms of the homotopy fibers of the original maps. Restricting our attention to the connectivity of these maps, we recover the classical Blakers-Massey Theorem.homotopy excisioncellular inequalitytotal fiberhomotopy localizationtext::journal::journal article::research article