Ask the wise men of many cultures, and they will tell you that all is temporal, all will pass, there is nothing in this world to cling to, only to transcend.
Ask a sage of the Torah and he will tell you it is not true. The vanities of time, the failures of life, they all pass as clouds on a windy day, but truth lives forever.
This is the meaning of the thirteenth of the thirteen principles of our faith, the belief that those who lived true lives will live again, in a real and corporeal way. It is a rejection of temporalism, a confirmation that there are things in the world that really matter, that have endless meaning and absolute purpose.
Whenever a G-dly act is performed, all involved are elevated beyond time. Save a life–you are Noah saving the entire world. Feed weary travelers–they are the angels coming to visit Abraham and Sarah. And Abraham and Sarah are hosting them with you.
In fact, all those who had truth in their lives are here with us today. It is only that we are so much a part of this river of time, we cannot lift our heads to see above it.
Only when the falseness of the world will be ripped away and all is elevated to a place of truth, then we shall all see each other, together once again.