Is there a difference between 凡事 and 所有？
First, a little background: Most of 鲁迅's writings  were done in the middle of 白话文运动--to write with plain Chinese instead of arcane literary Chinese. Unfortunately, 鲁迅's way of using plain Chinese was not as influential as chairman Mao's, most of which actually have Huananese origin. From today's point of view, 鲁迅's "plain Chinese" is rather idiosyncratic.

凡事: Under most/all circumstances.

凡事，指不论什么事；所有的事。语出前蜀 魏承班 《谒金门》词之二：“愁倚画屏凡事懒，泪沾金缕线。”

Source: http://baike.baidu.com/view/3066308.htm



所有: 整个;全部；一切。有时也指一定范围内的。All, all within a scope.

Source: http://baike.baidu.com/view/1006583.htm