Dealing with the question every parent has to answer—Will my dog/cat/bird/fish/any-kind-of-pet go to heaven? Is it dead forever?—this is one of the best meditations on the old question of the relationship of earthly to eternal existence I’ve ever read:
The whole thing is here.
Hard as it is to comprehend not missing the things of this world which we love, our hope -- not our hopeful feelings, but our objective hope -- lies in the promise that we will not. And if we don't, it won't be because our loves have somehow been anesthetized, but because we will find their objects, and more, in the face of God.
I think the suggestion that our loves will be anesthetized is sometimes a huge mistake in our understanding of heaven. To be told that we just won’t care any more about the pet that we loved so much, to say nothing of the possible eternal loss of people we’ve loved, is no consolation whatsoever.
The instinctive intuition of children that death somehow must not be forever is striking. From the time we become conscious we are simultaneously in time and outside it, which is the whole human problem in a nutshell.