Board Thread:General Discussion/@comment-28431168-20160617130858/@comment-30438304-20170106170523

@Capitano Nox

We can not know, not only because good and evil are a relative concept( in my opinion), but because there just isn't enough information about him.

@Alexkdk

While it is likely that Sans and Papyrus weren't alive at the same time when Gaster was, we still don't have any concrete proof that it is true.