Mia Freedman has identified a fear we've all felt.

A couple of days ago I came home early from work to find a man I didn’t know outside my house with a ladder propped up against the roof. Probably, it was the roof guy, I thought. Nothing to worry about.

But what if it wasn’t? Should I just trust that it was?

What followed was an experience and internal dialogue every woman has probably had at some stage; many times most likely. It stayed with me afterwards – not because it was a particularly frightening incident or very different to the hundreds of similar experiences like that I’ve had. Had I not decided to post about it on Facebook I would not have given it a second thought.

But because in explaining it to my husband, it made me realise how all women and girls exist on this level and most men have no idea that we do.

Here’s what I wrote on my Facebook page:

In less than 48, it was  shared 1500 times, received 10,000 likes and reached 700,000 people. There were thousands of comments from women sharing their own similar thought processes and protective behaviour they are barely even conscious of.

Many many women tagged the men in their lives so they could understand how we feel on most days of our lives.

Some commenters missed the point and were angry that I was accusing tradies or all men of being murderers or rapists. No, no, no, no, no.

Not all men. And not all tradies! This was not about any one man and certainly not about any occupation.

I was simply articulating the vulnerability I felt as a woman who could be physically overpowered by pretty much any man who chose to do so at any time if there was nobody else around.

Scroll through to see the responses to Mia's post from women across the world.

Yes, 99.9 percent of men are good guys. But we can't tell who the .1% are just from looking at them or when they're walking behind us in the street.

And it's not just tradesmen. It's cab drivers. Uber drivers. Men in elevators or carparks or parks or empty train carriages or the streets around our homes and schools and the places we go to work and have fun. Anywhere that we're alone in an enclosed space or, in fact, any space with a man we don't know and nobody else around. It might be a stairwell. An empty beach. A unisex bathroom. Our own home. Violence against women does not discriminate. The men who rape and murder women do not look a certain way, they don't wear signs or glow in the dark. If only.

So to preserve our safety - and our lives - we must be on constant alert for signs and signals. We must map out imaginary escape routes. We must scan the area for other people who could potentially help us if we screamed. We must walk to our cars with our keys held between our fingers in case we have to fight off an attacker. We must look in the back seats of our cars to make sure nobody is there.

The thing is that this isn't even a big deal. It doesn't take a great toll, this vigilance. We don't walk around feeling terrified. Not even close. Most of the time we're unaware we're even on alert. It's a sixth sense that's baked into being female. Like an app running in the background of our lives.

Listen to our Mamamia Outloud team debate women and safety in public spaces. (Post continues after audio.)

Because we've been conditioned to scan our surroundings for risk and danger since we were girls.

We have the names of other women seared into our minds: Jill Meagher. Anita Cobby. Margie Edwards. Stephanie Scott. Masa Vukotic. Janine Balding. They walk with us on a cellular level and pop into our heads unbidden when we have to make decisions about which way to walk home, where to park our cars, whether to jump out of a cab at the lights because the driver seems a bit....not right, whether to get the uber guy to drop us a few houses away from where we actually live and wait until he's gone before we walk inside.

They are with us when we hear someone walking behind us in an empty street or when we're alone in the house with a man we don't know.

It's this silent thrum of awareness of our own vulnerability that men would never ever realise exists for us.

So what am I trying to say? I just want men to know how that feels. Not because it's their fault. Of course it's not. Most men are good. But explaining to them how vulnerable we feel sometimes and what it's like to walk through our daily lives on some level of alert is something they should know if they want to better understand women.