John Stuart Mill, who picked up Ancient Greek and Latin around the age of five (before writing On Liberty), would have been right behind Michael Gove bringing back languages – ancient or modern – for seven-year-olds. But hold it right there, sceptics will say. Isn't this the same John Stuart Mill who admitted to having a nervous breakdown around the age of 20? Doesn't this prove that our delicate English monolingual brains really can't take too much foreign gibberish? That by learning other languages, we risk a descent into madness? The cure – as Mill himself suggested – is more Wordsworth. Stick to English.

There is a more caring version of the sceptical case. Let the high-flyers do languages. Languages are a luxury – they are the turbo-drive, an optional add-on, a fashion accessory. Meanwhile, the hoi polloi, the masses, should really stick to English and maths. They will be happier that way. It's less of a strain for them.

All hogwash, of course. And condescending hogwash at that. The argument is over and the verdict is in. The fact of the matter is that learning languages builds bigger and better brains. Well, do you want a better brain or not?

Personally, I got into languages under the nefarious influence of wine, women and song (the woman was Brigitte Bardot and the song was "Je t'aime, moi non plus"). And I would add, Je ne regrette rien. But now neuroscientists have shown that learning a second language enhances brain power across the board. You can actually see the synapses going forth and multiplying.

A second language builds cognitive potential, not just linguistic ability. It's like a workout at the gym for your mind. So, for example, if you want to get better at long division, you'd do well to learn Spanish. The brain is like a rainforest: an intellectual eco-system in which all the different faculties are interdependent. Adding a soupçon of parlez-vous enriches the parts that maths alone cannot reach.

Recently, I saw a bunch of kids aged nine and 10 (from St Faiths School in Cambridge) learn Ancient Greek in a day. Well enough, at any rate, to give a dramatic presentation of an epic poem several thousand years old by 3 o'clock in the afternoon. It was "Arate pulas" – "Lift up the gates" (which became Psalm 24). It was like that Tom and Jerry cartoon in which Tom becomes a concert pianist in three easy lessons: one note, two notes, then a whole Rachmaninov piano concerto. Lifting up the gates summed it up neatly. Any language opens a portal into a parallel world. Suddenly, these kids really were conquering heroes.

Dumber and dumber or smarter and polylingual? You choose.

Andy Martin's latest book is 'The Boxer and the Goalkeeper: Sartre vs Camus'. He teaches at Cambridge University