The curiosity of preschoolers is wonderful, in many senses of the word. Certainly, they are, themselves, full of wonder, and it is marvellous to behold. Frequently, however, it is a wonder where The Prata Boy gets the things he comes out with, and I wonder how to respond.

Maybe nine months ago, PB was paddling in a wading pool when a woman stepped in to join us. She would have been around forty years old. She'd seen me struggling to divide my attention between a toddler and a baby in the water, and had come to entertain the toddler on my behalf. Imagine how I felt when The Prata Boy piped up to ask her where her children were.

"I don't have any children," she answered mildly. "None at all!"

"PB..." I cautioned, but she gave me a smile and a shake of the head to let me know it was ok.

"I'm married," she continued, "but I don't have any kids. But I like kids. Very much. I like to play with kids like you in the pool. Shall we sail your boat?"

"Yes," PB affirmed, but his attention hadn't been completely redirected, because about twenty seconds later he piped up and said, "Don't worry. You might start growing a baby soon."

I died. But the woman just said, "Well, we'll see, won't we?" And that was that.

It is hard to explain to him that these questions can cause offense, when they never seem to cause any offense.

"Why do you have that stick?" he asked a visually impaired man at the bus stop, and the man smiled warmly, explained his situation, and demonstrated his use of the stick.

"Why are you using that wheelchair?" he asked a woman at the supermarket, and she, likewise, gave a warm smile, and explanation, a demonstration, and a sweetie.

"Why do you have darker skin than us?" he asked a friend, who laughed and called him cute and turned into an enthusiastic tourism advertisement for her country of birth, right there on the spot. "Why does she have the same colour skin as you?" he asked in followup, loudly pointing out a random passer-by, and the two waved a cheery hello in their native language before my friend explained that they came from the same country.

"But you shouldn't really go around asking people that kind of thing," I tell him. He wants to know what kind of thing, and why not? Both questions prove more difficult to answer than they seem.

Last week I emailed backwards and forwards with Mel, she (whether she knew it or not) playing the mother and me channelling my inner preschooler. What is it about calling something "kosher" in the colloquial sense (as opposed to the religious sense) that offends some people? What about using the words "God" and "Jesus" as exclamations? Where is the line between those who are allowed to use a word or make a joke and those who are not? Why do Mel and a stranger dance around the fact of their Jewishness? And when does it become not ok for a little boy to innocently break these types of taboos, which, to him, don't yet exist at all?

When do they start existing? And how... no - why am I helping to bring them into existence?

My experience of infertility tells me that, whilst it can be awkward (especially in the initial stages) to broach problems and differences, in the long run, it is more awkward to let them sit between people as an unspeakable divide - the metaphorical white elephant, to whom we often refer. Moreso, perhaps, for the obvious differences - if you use a stick, or a wheelchair, or have a certain colour skin, it's hardly a secret, so what's the use of being coy? What message does it send when we are? Is there something wrong with being unable to see or move like the average person that makes us hush up, as if it's a shameful non-secret? Is there something wrong with having a certain colour skin, or being married, without children? The important thing, surely, is not whether we observe that somebody has one trait or another, but how we let this change our perception and treatment of them afterwards.

The Prata Boy gets away with it because, at four, he observes these traits completely without judgement - either perceived or actual. Over dinner he asks Mr Bea what country he comes from. "Australia! You know that," Mr Bea replies with surprise.

"Well, but, how come you have darker hair and skin and eyes than the rest of our family?" PB wants to know. He wants to know, but he doesn't care, as such. Dad is still Dad, even if he goes to the hairdresser and comes back hot pink. In which instance, the wonder would be mostly mine. "Who is this man I thought I knew?" I would be asking myself. "Suddenly I have no idea what to say to him."