As both a parent and philosopher, the question you raise about appropriate religious upbringing is one I thought about quite a bit as my children, now 19 and 22, grew up. The heart of your four-part question is this: How, if at all, should the parents’ religious convictions influence the religious development of their children? While the influence of teachers, friends, and the general culture on a child’s religious outlook is very great, the religious (and here I include non-religious) upbringing by parents or the primary caregivers, whether intentional or not, is fundamental. It certainly warrants careful consideration by parents and prospective parents leading up to and throughout the period of their children’s formative years, and even beyond. I would argue that if there is a right answer to your question, it is the same answer for all four of the scenarios you raise.

The approach I’ve tried to follow is that one should educate one’s children about the whole range of religious beliefs, practices, and institutions. That can include bringing one’s children in contact with religious practices, such as services and ceremonies, but it also includes providing children with the history of the various religions of the world, as well the culture and politics of those religions. At the same time, in order to ultimately be in a position to evaluate this information, children need to develop their thinking and reasoning skills as well. The nature and quality of one’s general education is also very important. This is clearly a tall order, and no one should expect to be able to accomplish it in anything like a complete and comprehensive manner. Still, it is an ideal worth tilting toward. One’s children should have the relevant information and reasoning skills to ultimately make their own decisions about matters of religion. It should be possible to do this while parents continue to express and act on their own convictions relating to religion, bearing in mind that parents’ actions can have a particularly profound influence on the child.

At the start of his Meditations on First Philosophy (1641) Descartes notes that he was a child before becoming an adult, and that as a result, many of the beliefs he acquired were not the result of well-informed rational reflection, but largely the influence of his education and upbringing. He resolves to meditate on all his past beliefs and determine whether any of them can be established as certain. These beliefs include his beliefs about God. While Descartes didn’t canvass the diversity of religions in the world at his time, he did attempt to use careful reason and reflection to determine what he ought to believe. Descartes’ example suggests that determining what one ought to believe, both about religion or anything else for that matter, is a life-long pursuit, one which we can prepare children for by educating them as critical thinkers and questioners.

Another philosopher from later in the modern period of philosophy well worth reading is David Hume. Almost all of Hume’s writings relate in one way or another to religious belief, but the work most relevant is his Dialogues Concerning Natural Religion, published posthumously in 1779. Hume treats religion as a natural phenomenon which we can study and analyze as such. What he calls “natural religion” is as much a phenomenon of the natural world as are the flora and fauna. A contemporary philosopher influenced by Hume is Daniel C. Dennett, whose recent book Breaking the Spell (2006) argues for the importance of a scientific understanding the influence of religion on human behavior. For an overview, a recent lecture by Dennett which treats the very issue you’ve raised, is available at: http://www.ted.com/index.php/talks/view/id/94.

While I’ve suggested that parents should strive to bring it about that their children develop in such a way that they ultimately can make their own decisions about what, if any, religion to adopt, it’s clear that this is not an easy thing to do. For many parents, religious beliefs are closely intertwined with other central moral, political, and social, esthetic and even scientific beliefs. This is also true of friends, teachers, and others with whom the child comes in contact. When my daughter was in grade school, in a conversation with two other children, one child asked the second, “Where do you go to church?” The second replied: “We don’t go to church, we go to synagogue.” The first student then asked my daughter the same question. My daughter replied: “We don’t go to church.” So the first child inquired further: “Ah, so you go to synagogue!” My daughter replied: “No, we go mostly to restaurants.”