...has an equal and opposite reaction. It's an irrefutable law of physics (at least for now, although we did think that nothing could travel faster of light and that is now being questioned...)
It could also be a law of coalition politics - the Tories and Lib Dems are able to press ahead on things on which they agree and give way on other things with with which they don't. Earlier on Facebook, Caron Lindsay posted a link to this Huffington Post piece by Louise Phillips which deals with exactly this. Every time you hear a Lib Dem talk about increases in personal allowances remember that Tories gave up plans to increase the Inheritance Tax Nil Rate Band, (re-)introduce Married Couples Allowances or remove the current 50% "Additional Tax" band.
Caron being Caron, though, she didn't leave it at a just a Facebook link - she's written her own excellent post on the subject. She succinctly points out that the reduced tax has been swamped by people's experience of high inflation and wonders whether it is better presenting the facts as practical examples of what this could have purchased rather than just pounds and pence.
As inflation comes down and this year's annual allowance increase (whether that be the £8,105 previously announced or a new, higher figure urged on Osborne by Lib Dem ministers) kicks in, she'll have to think of bigger examples of how the Liberal Democrats are making a positive difference to people's take home pay, and their monthly finances.