Preaching to the converted: Corbyn performed well, but his omissions were glaring and he gave the impression of preferring protest to power

It is said that a leader’s speech must appeal to two audiences: the committed activists in the conference hall, and the much wider body of sceptical voters outside. On both counts Jeremy Corbyn acquitted himself unexpectedly well, though his activists – this youthful army of political ingénues he has crowded into his party – found more in it to get worked up about than did the public.

Mr Corbyn’s was a more poised performance than at the TUC conference just a matter of weeks ago, which will cheer the Corbynistas, still something of an insurgency within the Labour establishment. So confident is Mr Corbyn that he has even taken to describing himself as “authentic”, a rare flash of conceit in such a modest man. He made the best of his time on at least one issue – his appeal to David Cameron to intervene with Saudi Arabia to spare the life of a dissident, Ali Mohammed Baqir al-Nimr. That was clever but also principled politics.

The attacks on the Tories were well targeted, but that has never been enough to get Labour into power. He countered the Tory jibe that he represents a threat to family security, an absurdly extreme claim in any case. Yet the voters know full well the Tories’ weaknesses on compassion, on social justice and the NHS, and while they dislike them for such nastiness, they also value their reputation, deserved or not, for economic competence. Tony Blair’s achievement was to show how social justice and economic competence can be combined, and every act of his leadership was geared to that purpose. In repudiating Mr Blair’s illegal adventure in Iraq, Mr Corbyn has also silently terminated that essential social democratic mission for his party.

So Labour’s new leader has repeated the classic error of bolstering Labour’s strengths – the party of protest for those on benefits and of trade unionists – but failed to do anything to neutralise Labour’s critical weaknesses. There was no sense that Labour had gone down to a disastrous election defeat just months ago because its platform was too left wing. Ominously, this speech was simply silent about what a Corbyn-led party and government would actually do instead.

It is worth listing the areas where Mr Corbyn, deliberately or not, said nothing – the budget deficit, for example. Where Ed Miliband forgot to talk about it a year ago, Mr Corbyn seems to have deliberately avoided it, though his shadow Chancellor has made some broad statements about how they will tackle it. Immigration, surprisingly, was another area Mr Corbyn left at the level of principle rather than practice. He was brave to say that Britain should offer a welcoming hand to refugees from Syria; but failed to say how many this country should accommodate.

On Trident, Mr Corbyn did state his long-held view that we should be rid of it, but we are none the wiser about what his government would actually do. On Europe too, there was much talk about workers’ rights but a failure to repeat the solid pledge of his shadow Foreign Secretary, Hilary Benn, to campaign to stay in the EU.

Addressing the “commentariat” directly – unduly flattering to it – he proposed a new political language where compromise is not synonymous with weakness and honest differences with “split”. He is right about that; but plain wrong to suppose that Labour can meander towards the next election with nothing more than discussion documents and agreements to differ to put before the people. This early in his leadership Mr Corbyn can get away with it – but not forever.