In the supermarket the other day I found my way blocked by a woman pushing her elderly mother in a wheelchair. The old woman was looking at the floor and muttering to herself, barely aware of the world around her. The daughter was straining to engage her in choosing what type of dessert to buy from the yoghurt section. Eventually, after several attempts, she interpreted a downcast grunt as signifying a desire for strawberry flavour. As I tried to make a discreet lunge for the creme fraiche, she looked up at me with drawn, bloodshot eyes and meekly apologised.
A few months ago I might have hastily grabbed the tub of creme fraiche and bustled along the aisle asking myself a dozen questions about why she bothered to take her mother shopping, because clearly the doddering old fool barely knew what time it was, never mind what type of yoghurt she'd like. But now I connected with her, at least fleetingly, as someone looking after a disabled relative, determined to maintain as normal a life as possible even when it seems to rub against logic. Besides, it's much harder to be scathing about other people's disruptive habits when you've seen scornful cast looks at your own child because he insists on touching every can of beans in the aisle, or stops to line up the paracetamol boxes at the chemist's counter.
Here's one of the unforeseen side-effects of having an autistic child: it's made me a more tolerant person. The more I learn to cope with Euan's behaviour, the more I appreciate how many other people out there are managing to get by in spite of neurological conditions, traumatic backgrounds, bouts of mental illness or physical disabilities. And it's not a question of "overcoming" these problems: people with dementia, say, will never overcome their condition (indeed, it will eventually overcome them), but that doesn't mean that those little acts of kindness that make their lives more bearable are pointless or unappreciated.
And there's a social dimension, too: in joining autism support groups we have met all kinds of different people who have been thrown together by a quirk of genetics. As you get older it's easy for your focus to narrow: to seek the company of people with the same social status and attitudes as yourself. In a perverse kind of way, having a child with a disability is an antidote to that, because it interferes with the ability to choose your associates. In the French film Le Huitieme Jour, a professional man moulded into a high-achieving routine realises what a narrow groove his life is stuck in when he has to look after a man with Down's syndrome.
So if I were a politician, this would be my manifesto pledge: everyone should be compelled to spend one day a month with a disabled person. I believe it would spark a benign revolution in people's social understanding. And make supermarkets much more pleasant places to shop in.