There are about 170 million cats and dogs in the U.S. that have found a place in the homes of American pet owners, according to the 2009-2010 National Pet Owners Survey.

Probably most of them have also found a place in their owners’ hearts. And anyone who’s ever had to say goodbye to Fido or Fluffy has wondered if their beloved pets will be waiting for them in heaven.

The fate of our four-legged friends — whether they have a soul, whether they'll be in the afterlife — has occupied the minds of Christian thinkers ever since the days of St. Thomas Aquinas and St. Augustine.

Three recent books try to answer the question, and affirm a special relationship between humans and animals — one that does not end with death.

Do animals have souls?

Author Ptolemy Tompkins tracks the history of the relationship between humans and animals in the new book, The Divine Life of Animals. Prompted to write by the death of his pet rabbit, Angus, Tompkins looks to the ancient past for the best models of animal-human interaction.

“Pre-modern cultures ... were apparently able to see animals as undying spirits dressed, for the moment, in mortal bodies,” he writes.

The idea is to recover that “new-yet-old vision” that “will allow us to see (animals) as the genuine soul-beings they are and always have been.”

In Tompkins’ view, Western culture is based on Christian theology, which in turn is heavily dependent upon ancient Greek thought that has a hard time accepting the idea of animal souls dressed up in mortal bodies.

Put another way: humans are rational, animals are not. Tompkins doesn't buy it.

“Through the Greeks, we allowed ourselves to kind of remove ourselves ... from our participation in the life around us,” Tompkins said in an interview. “With each step of knowledge, we understand the world a little better, but at the same time, we get a little bit away from it.”

The emphasis on reason made it easy to deny the idea that animals have a soul. And without souls, animals could not possibly get into heaven. It’s an idea that Tompkins, a self-described “unconventional Christian,” solidly rejects.

“Not only humans, according to the traditional view ... are potentially divine,” he writes, “but all of nature is as well.”

Do animals go to heaven?

The Bible isn’t much help, says Laura Hobgood-Oster, professor of religion at Southwestern University in Georgetown, TX, who like Tompkins says the question of animal souls was not always an issue for Christian theology.

Although there are plenty of mentions of animals in the Hebrew Bible — the snake in the Garden of Eden, Noah and his animals on the ark, Jonah and the giant fish —  the New Testament is relatively silent on the matter.

Hobgood-Oster’s upcoming book, The Friends We Keep, places the animal-human relationship in the history of Christianity.

“It seems that the question of animals and the soul was much more plausible ... in Christian history up almost until the Enlightenment or up into the Reformation,” she said in an interview.

Eventually, “all the animals started to disappear (from Christian theology).”

Hobgood-Oster doesn’t accept the idea that only humans can possess a soul.

“In the last 20 or 30 years, I believe we’ve seen these questions raised anew,” she said — questions that challenge “the traditional theology about humans being the only ones who matter, or humans as the only ones with souls.”

And if humans aren’t the only ones with souls, they’re probably not the only ones in heaven, she said.

“There does not seem to be any indication (in Scripture) ... that there is a special human exclusion (in heaven),” Hobgood-Oster said.

Will animals be ‘saved’?

Reluctance to the idea of animals in heaven persists in some Christian circles. Last year, Franciscan Friar Jack Wintz published the book, Will I See My Dog in Heaven? This year, he answered his own question with a new book, I Will See You in Heaven.

Taking inspiration from his order’s founder, St. Francis of Assisi, who’s also the patron saint of animals, Wintz presents biblical evidence for the inclusion of animals in heaven.

In the book of Genesis, he writes, both humans and animals live in peaceful harmony — “a wonderful and insightful glimpse of the paradise that is to come,” he writes.

“It makes sense to me, therefore, that the same loving creator who arranged for these animals ... to enjoy happiness in the original Garden would not want to exclude them from the final paradise,” he writes.

Wintz, who lives in Cincinnati, also found inspiration from the New Testament, saying that “Jesus delighted using images from nature.” It’s all evidence that suggests “the gospel message will have a saving impact upon the whole family of creation, and not simply on the human family.”