A chance to see who the real believers are...

It is not that they attract a crowd – the House, again, was discreditably empty yesterday. It is the fact that unwhipped votes smoke out our politicians’ personal convictions.

We get to see who embraces what principle, who holds what little prejudice, to what extent. We discover who the real believers are, left and right, as opposed to those who simply hold views for reasons of careerism and craven terror of the Whips.

As MPs started to discuss the Human Fertilisation Bill yesterday Iain Duncan Smith (Con, Chingford) and Geraldine Smith (Lab, Morecambe) ran up the flag for instinctive conservatism.

Vote: MPs in the House of Commons last night

They argued that it was loopy to encourage IVF families not to have male role models. They spoke up for fatherhood.

Their counterparts proved to be Health Minister Dawn Primarolo and a ginny-voiced urbanite called Emily Thornberry (Lab, Islington S).

These two led the charge in support of lesbian couples and their right to have IVF babies without being required to surrender the name of some father figure to officials.

On a day when the House also debated abortion – the leading anti-abortion reformer Nadine Dorries (Con, Mid Beds) had dished herself up in a bright pink silk blouse – the IVF/fatherhood debate had a certain poignancy.

At least the discussion here was about people who wanted pregnancies rather than about those who wanted to dispose of them. The fatherhood debate was caused by a Duncan Smith amendment to some pro-lesbian legislative tweaking by the Brown government.

It was a pretty minor point to merit three hours of prime time in the Commons. The Government’s little measure was scarcely more than symbolic.

So was the opposition from the likes of IDS and Morecambe’s Miss Smith.

Social attitudes are changing from ebb to flow.

Would the river hasten towards IDS or was it still running with the anything-goes Left?

From the moment Mr Duncan Smith began his defence of fatherhood there was tutting and tskking from some quarters, among them Chris Bryant (Lab, Rhondda).

IDS argued that families-with fathers have fewer social problems.

The absence of a father was just as bad for girls as boys. Fatherless girls had less concept of "empathetic, non-conditional love", argued Mr Duncan Smith, and therefore strayed towards sex at an earlier age.

An interesting theory and pretty persuasive.

But do we really want to demand that officialdom has greater powers to boss us about and to demand the name of some father figure?

Oddly, no one attacked the IDS position from this direction. Instead Miss Thornberry and Co played the "discrimination" card.

They still adhere to the politics of victimhood. Miss Thornberry, who is magnificently county for an Islington Member, kept her left hand held behind her posterior as she spoke.

Her right hand was placed to her fore, its little pinky extended in a gesture of genteel horror at the very thought of anti-gay prejudice.

She disclosed that she had been brought up by only a mother. "And I’m all right," she barked. Indeed you are, scrumptious one.

Miss Smith, a plain- spoken Northern lass, told gravelly-jowelled Miss Thornberry that she was speaking a load of cobblers.

Miss Thornberry wobbled with superior amusement at her working-class assailant.

"I am very concerned about some of the attitudes coming from the benches opposite," she said, voice gooey with matronly disappointment.

Sir Patrick Cormack (Con, S Staffs) let blast: "In Staffordshire it is thought normal to have a father and a mother.

"Is it thought normal in Islington to have two mothers?"

Miss Thornberry, along with jovial Mr Bryant and the appallingly creepy Evan Harris (Lib Dem, Oxford W), raised their eyes to the ceiling in disbelief.

They seemed to be thinking: how could such old-fashioned views persist?

Social conservatism certainly used to be old-fashioned. But with every week it feels that the more dated attitudes seem to be found on the Left.