My cat is used to roaming outdoors but my flat has a shared balcony — should I let him out?

Speaking from what we see rather than from principle: the specific situation you describe is one I would not allow, and the reason is the setting rather than the general question.

A cat who has roamed in the countryside has learned that environment — where the roads are, where the boundaries are, how to get home. Moved to an urban building on a second floor with a shared entrance, none of that knowledge applies. He does not know the roads, does not know the territory, and does not have a reliable route home.

The first weeks after a move are also exactly when cats go missing, because they have no established territory and will often try to travel back to the previous one.

So whatever you decide long term, the immediate answer is a period indoors while he settles — several weeks at minimum. That is standard advice after any move and it is not a permanent decision.

The middle options, which is where most people in flats end up:

Harness and lead. Genuinely works with many cats, especially if started young — and at six months you are well placed. It takes patience: harness indoors first, over days, then short trips. Never attach a lead to a collar.

A secured balcony. Netting or mesh enclosing your own balcony gives outdoor air, sun and smells with no escape route. This is common in cities and it transforms an indoor cat's day.

Supervised time outside in an enclosed yard if you have access to one.

A catio, if the building allows any structure at all.

The shared balcony is a real hazard regardless of what you choose — a door propped open by a neighbour is a route to a stairwell and a street. Worth a conversation with the neighbours whichever way you go.

On the ethics, since that is the part making you uneasy: it is a genuine trade rather than one obviously right answer, and the balance differs by place.

For outdoor access: more stimulation, more exercise, more natural behaviour, and generally fewer problems with boredom-related behaviour and weight.

Against: roads are the dominant cause of death in young outdoor cats. There is also fighting, disease transmission, poisoning, getting shut in a shed, theft, and predation of local wildlife, which in some places is a serious conservation issue.

Attitudes vary hugely by country — in some places indoor-only is the norm and outdoor access is seen as irresponsible, in others the reverse.

What is not in dispute is that an indoor cat needs the stimulation designed in deliberately: vertical space, window views, play sessions daily, puzzle feeders, and things to climb and scratch. An indoor cat in a bare flat has a genuinely worse life. An indoor cat in a well-arranged one does not.

Two practical things worth doing now regardless of the decision: microchipping and registering the details, and a collar with a quick-release buckle.

The chip is what gets a cat home if he ever does get out, and the number of animals brought in with a chip registered to an old address is depressing. Check yours is current.

And if you go the harness route, do not take him out until he has been in for those settling weeks. A cat in a new place on a lead can panic and slip a harness, and then you have the outcome you were trying to avoid.