Risks for Corbyn over nuclear stance
There is a big difference between holding fast to your principles and making a political party work in practice.
Jeremy Corbyn has succeeded in the first part for all of his political life. And arguably that's what won him the Labour leadership election.
But on this last day of conference, which has not been the bloodbath that many feared, principles and practicalities are clashing with full force.
This morning, Mr Corbyn told me explicitly, indeed with some irritation, that there was no way that he would ever use nuclear weapons because they are "immoral".
That's not that surprising perhaps, given his beliefs, but his situation now is different - he wants to be prime minister.
His position on ruling out taking such action as a last resort has immediately been criticised by not one, not two, but three of his shadow cabinet.
They haven't just rejected his view, but are angry that he has pre-empted the results of the policy review he wants the party to carry out.
And as the conference confirmed this week in any case, the party's policy is currently to keep nuclear weapons.
He also told me he doesn't think "immigration has been anything but a plus" - at almost exactly the same moment that the new Shadow Home Secretary Andy Burnham was on his feet in the conference hall saying that immigration has "made life harder in our poorest communities".
This might be the new politics, where disagreements are welcome.
But there is a risk what has been a far smoother conference than expected leaves the party in a state, not of open debate, but of open dispute.
For the public there is an old danger that a party who can't agree amongst themselves seems not interesting, fizzing with new ideas, but out of control, and unsure what they stand for.