I am prepared to be told IABU but I am having a 'disagreement' with DH and would appreciate the MN view 
DH has been looking after the DC this week and periodically has been going into the front garden with DS1 to play football and leaving DS2 in the house by himself to watch telly (DS2 does not like football!) He has been closing the door to keep the heat in the house. He says he has been checking on him regularly (which I don't doubt he has) and DS2 can open the door and go out if he wants them but I still have an uneasy feeling about it.
DH's argument is that it is only like being upstairs (for example, we have been known to stay in bed and have a snooze in the mornings whilst the DC are downstairs) when he is downstairs but my argument is that if he falls over/hurts himself etc you could hear him cry/scream whereas you can't if you are outside.
IABU?