For teenagers protesting about climate change, it’s a simple black and white issue. For teenagers most things are.

The process of maturity – a process which should never really stop – is the growing realization that very few things are as black and white as they seemed when you were a teenager – that there are nuanced, sometimes difficult, shades of grey to be negotiated.

This is why we are right to be suspicious of zealots, extremists and simplifiers. A protesting teenager is an idealist – a fifty year-old who sees things in simplistic terms and talks in sound-bites is a dangerously immature adult who should not be given unsupervised access to a whelk stall, let alone a country, a corporation or an NGO.

Don’t get me wrong – there’s a place for idealism and tackling climate change is critical, even, quite literally, vital. It’s good to see young people getting involved and I hope that many of them will stay the course, whether it’s changing behaviours or developing the knowledge and skills to resolve the technical, economic and political barriers to change.

There’s a place for idealism, but idealism is not enough. How many of our current problems are caused by idealisms which fail to take account of complex systems or human frailty?

The internet is a classic case of youthful West Coast idealism which simply didn’t take account of the possibility that people might use the technology for pornography, grooming, stalking, deception, fraud, propaganda or abuse as if the appetites for money, sex and power would simply vanish from the human psyche at the site of a keyboard. “Don’t be evil”, said Google. Yeah, right.

You could say the same about any number of idealistic projects: the EU – created to constrain power only to become a magnet for those who sought power without accountability; charities created to relive suffering,  which end up facilitating corrupt and bloody regimes and exploiting the people they are meant to protect; the “gig” economy – meant to free up work, but abrogating its responsibilities to the level of a Victorian sweat shop.

There’s a place for idealism, but idealism can only ever be the spark that creates the possibility of change – it isn’t change – it isn’t the engine that drives change – it isn’t even the fuel that drives the engine.