When it comes to parenting there are our own truths and there are indisputable facts.
Bed time routines, weaning techniques, re-useable or disposable nappies, whether to allow sweets or not; these are our own truths, developed out of the hard slog of simply bringing up children.
The fundamental mistake most of us make is assume our own truth should be applied as a general way to go about things: I do a strict bedtime routine with my kids, lots of my friends do too, therefore it's the correct way to go about things.
It was this attitude I encountered when my book on shared parenting was published. It concludes that men don't do anywhere near the amount of childcare - either in or out of working hours - that we've previously assumed.
I received a number of emails and social media messages from parents who said what I'd written was wrong. They'd shared parenting equally, some of their friends did too, so I must be making it all up to get a reaction.
Of course some families share parenting equally and those parents are likely to have friends who do things a bit like them.
What they were doing was applying their personal experience, and assuming it was generally true across all parenting. The sad, but real immutable truth is that parenting isn't anywhere near equal in the UK.
According to dispassionate numbers from the Office for National Statistics, the number of men becoming full-time stay-at-home dads has only increased by 6,000 men over the last ten years, compared with 44,000 fewer stay at home mums.
The number of men switching to part-time work has increased by a minuscule three percentage points, and is matched by only a similar increase in women going part time. The proportion of women working full time hasn't changed at all in a whole decade.
Outside of working hours, the same pattern emerges. Far from men taking up the cudgels of childcare in great numbers, women still do twice as many hours of childcare and related chores outside of working hours as men do. That has barely changed in a decade too.
These are facts, not personal truths.
It is these well researched immutable truths that should inform personal, political and academic practices on parenting, and particularly policy making, not a few parents' personal experiences posted as comments on newspaper websites.
Even the director of a fatherhood think-tank wrote to challenge my claim that women are paid more than men, before children are born: "I seriously doubt that's true".
It made me sad to send her the spreadsheet from the National Office for Statistics that shows, very clearly, exactly that. Surely, they at least should have their facts straight?
Unfortunately, we're not even close to allowing immutable truth to influence policy.
UK government policy on parental leave, for example, has been set according to a generalised assumption that men want to take more time off, and work more flexibly, to be with their children.
Yet the simple, statistic-backed facts support the opposite conclusion: men aren't yet using even close to the wiggle room they already have.
Only 1,600 men have taken the legal right they've had for over two years to share of 26 week's parental leave with their partner. Over that same period, around 1.5 million babies have been born. One in three dads don't even take their full traditional legal entitlement to two weeks' paternity leave.
So why is the government creating more of what parents are showing by their practice they don't want, even if they say they do?
The answer is that what I call the 'new fatherhood myth' makes a good story. It gets the media excited and it makes us all feel good about how equal we are.
It prevents us facing up to the more unpalatable truth that progress towards parental equality is still painfully slow, and certainly nowhere near as far along as we'd thought.
All of which prevents personal and political action that - as my book illustrates, and the facts and research have clearly shown - would really create better outcomes for our children, for parents and for the workplace.
Gideon Burrows is author of Men Can Do It! The real reason dads don't do childcare (ngo.media, 2013).
Visit www.mencandoit.co.uk to buy in paperback, or on Kindle.
This article originally appeared on the blog of the Centre for Research on Families and Relationships.