Children are natural born philosophers. They are constantly looking for reasons, justifications and patterns, and their enquiry knows no bounds. Behind each answer they soon discover another question to ask. It is not long before they have dug down to some of our most basic beliefs and preconceptions and are asking philosophical questions, questions like: What made the universe exist? Where do right and wrong come from? and: How do I know this isn't all a dream? Once we become immersed in the details of our day-to-day adult lives we quickly lose sight of such questions. The average grown up lives out his or her existence within a fairly narrow envelope of concerns. But children have time on their hands, an inquisitive nature and no preconceptions. They are still open to the bigger picture. What is our reaction when children start to ask philosophical questions, and what should it be? Unfortunately, when Sophie asks, say, "Why did the Big Bang happen?" the temptation is usually to fob her off.

One way we do this is to insist that the pursuit of such questions is a foolish waste of time. Sophie may well receive the brusque reply: "It just did. Don't ask silly questions." If she learns that philosophical questions tends to provoke irritation, and perhaps even rebuke or ridicule, she may well stop asking them.

The other way we tend to fob children off is to take their philosophical questions more seriously but pretend that they have pat, easy answers. Religion provides a convenient crutch here, even for the non-believer. Where did the universe come from? God made it. Why is doing so-and-so wrong? Because God says so. These answers may satisfy the child, at least temporarily, but they are for the most part inadequate. Either they do not really deal with the mystery with which the child has begun to grapple, or else they replace that mystery with another that is no less perplexing.

For example, if Sophie asks, in the spirit of rational inquiry, where the universe came from, it will not do to reply with an air of authority that God made it, as if that conclusively settled the matter, especially if one's response to her next question — And where did God come from? — is to fudge or distract her with an offer of an ice cream. I am not rejecting religious explanations per se here. I am objecting only to their being used to stifle inquiring young minds. Why do we fob children off? There are many reasons. One obvious reason is that we don't know the answers ourselves and our ignorance can be a hard thing to own up to, especially to our own children.

Another reason is that the philosophical questions are pretty difficult to think about. Most adults are scarcely any more sophisticated in their thinking about them than is the average child. We know that engaging in some sort of debate with our offspring is likely to be hard, headache-inducing work and that we are likely quickly to end up out of our depth.

A third reason is that we can find such questions not a little uncomfortable to think about. And that is not just because some of them confront us with our own mortality and the possible meaninglessness of our brief lives. Philosophical questions can also induce a rather disturbing sort of intellectual vertigo. They may reveal that what we took to be the firm ground beneath our feet — what we thought was "common sense" or "just obvious" — is actually illusory. They may reveal that we are suspended over an intellectual void. To think philosophically is to think without a safety net.

Here's an example. Most adults in this country — to the extent to which they even think about the issue — would profess to find it "just obvious" that while killing and eating humans would be a moral outrage, killing and eating other species of animal is perfectly OK. Now most children will quite spontaneously question this moral belief at some point in their development. They find it intuitively dubious. And so they ask us to justify it.

The problem is that, as the philosopher Peter Singer has shown — it is an extremely difficult belief to justify (it won't do, for example, simply to say that pigs and cows are less intelligent than us: that would justify our eating mentally handicapped humans). In fact, it is difficult to avoid the conclusion that we are guilty of what Singer calls speciesism: a form of unreasoned bigotry against other species similar to racism and sexism. Indeed, it's hard to avoid Singer's conclusion that the slaughter of many billions of animals each year merely to satisfy our taste for a certain sort of foodstuff is a moral outrage at least on par with, say, the slave trade. It's not surprising, then, that rather than deal properly with the child's request for justification we find it more comfortable to fob them off (much as the child who questioned the legitimacy of the slave trade might have been fobbed off a couple of hundred years ago). We dismiss their worries about eating meat as silly and childish.

Either that or we attempt to shut down their line of inquiry with a glib religious answer: "God put the animals here for us to eat. It says so in the Bible." Whatever the reasons why we dismiss the child's philosophical question, we shouldn't, at least not in the long run. Here are three good reasons why. First, those who have either been conditioned out of thinking about such questions or else have glibly assimilated pat religious answers lead impoverished lives. Like a goldfish that lacks any sense of there being something beyond the glass walls of its bowl, such individuals have no real sense of the mysteries that lie beyond the boundaries of their day-to-day lives.

Secondly, and more importantly, those who have never taken a step back — who have lived wholly unexamined lives — are not just depressingly shallow, they are also potentially dangerous. Merely to slip into adopting the mental habits and unexamined assumptions of those around one is the mark of the moral sheep. A moral sheep may do the right thing. But they don't do it because it's the right thing. They do it because it's what the other sheep do. If the flock takes off in a more insidious direction — if it wanders into hatred and bigotry, for example — the moral sheep follows blindly along. A society of moral sheep is a very dangerous thing.

Thirdly, the skills that early exposure to a little rigorous thinking about the big questions can engender are both immediately transferable and highly valuable. Being able to formulate a concise argument, follow a complex line of reasoning or spot a logical howler are abilities that are always useful. At the very least such skills can provide a lifetime's immunization against the wiles of snake-oil salesmen and religious nutters.

Thinking hard about the big questions is an important part of life. It's part of what makes us fully human. We should not discourage children from asking such questions. We should actively encourage them.