Suggest opening with:

> There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.

> There is another theory which states that this has already happened.

This leads naturally into some discussion of the meaning of it all, etc.

If you want to include more of the works in your eulogy, I would suggest the “dolphins v. humans” quote (also mentioned above):

> On the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.

This would lead into a discussion of how your Dad was properly focused on the little joys of life, over the grand achievements and the mistreatment of others required to accomplish those.

Very sorry for your loss, good luck preparing your speech.