?? "whole as sum of parts" ... "big jump as sum of little jumps" ... ??? "jump" ?? ..."step" ?? .... ??? ..... "journey of 1000 miles begins with a single step" ... ?? ?? big steps vs little steps .... ???? .... ?? ....??? .... "longitudinal vs transverse" ??? .... ??? contrast as disappearing in infinitesimal limit ???? ..... ??? vs "wave equations" where it doesn't ?? ... ???? .... .... telescope ... longitudinal .... line-painting truck ... ???? .....