Just as canals and rivers represent difference, so too, perhaps, are sporting players.
ome seek to rein in freedom, to dam the eager flow to serve the design of others, just as the canal is hemmed in by locks and walls and bridges.
A construct of the logical head.
But the river flows freely where it wants, dictated by its own rhythm and pace, weaving hither and thither, deviating dizzily around seemingly immoveable obstacles.
A design of the pulsing heart. Which one would you choose?
All roads - and waters - lead to Lansdowne Road today. Two teams attempting to alter course, trying to find that elusive balance between the heady romantics and those devoted to Gradgrindian pragmatism.
James Hook - in 'Top Gun' terms more Maverick than Iceman - will retire this summer, an Osprey whose wings were rarely clipped.
He featured eight times in this fixture, representing ten per cent of his 81-cap, nine-year career, and the meetings almost serve as a microcosm of the gifted play-maker's time in red.
Half of the eight games he started; half of those he started at out-half, the other half at 12; half of the games his side won; half they lost.
His glass was, however, always half-full. One besotted by numbers might delineate a life stationed in the middle of the road, but Hook's career was anything but.
Three Championships - two with a Grand Slam appended - and a World Cup semi-final appearance brook no argument, even from him.
Though not always a winner, he won enough to ensure his life was a thrill to him. And more importantly to those who watched, too.
"I remember going to a testimonial for Neil Jenkins (fabled Welsh out-half and current assistant)," Hook recalls. "He'd over 80 caps for Wales and I didn't think I could get one cap never mind get near that level.
"There are a few things you might have done differently but then how else might life had turned out? So you can't really have regrets.
"I've won Grand Slams and been a British and Irish Lion. A lot of people wonder could they have done more but not me. I'm pretty happy."
Depending on how bad the incipient fury of Storm Ciara, there may well be a different look to this spiciest of rivalries; already, to the relief of many, there has been little of the faux pre-match trash talk.
Warren Gatland has exited stage left and taken his script with him; Wayne Pivac is now the lead but for him, the play will be the thing; Ireland, too, will not seek to bang their heads against red brick walls with unceasing violence.
Heaven forbid, a game of rugby may, perhaps, break out along the banks of the free-spirited Dodder.
"It's a little bit too late for me isn't it?" smiles the Captain Hook who, at 34, decided he didn't want to become Peter Pan.
"As a player, I would have loved to play under Wayne Pivac's style. But that's gone now. Gatland was successful in his way and they're trying not to forget that, just expand and adapt to the way the sport is going.
"They've got the players that suit that style and they showed glimpses against Italy. If they can perform and win this weekend they'll all be happy.
"The only criticism Gatland got was that the rugby was not enjoyable to watch. And his answer always was, 'Well, we're winning games of rugby!'
"But on the evidence I saw last weekend, the fans enjoyed seeing a little bit of rugby combined with a win."
Rightly or wrongly, Hook was regarded as a luxury item by Gatland, who preferred the more yeomanry traits of a Jones or a Priestland or a Biggar.
His last big chance was a surprise on the biggest stage of all; a late injury call-up at ten for the 2011 World Cup semi-final against France.
It was a game his side should have won, and Hook had kicks to win it; but it slipped away; in the following four years, Hook would win 23 caps but make only three starts as Gatland continued to view him as a jack of many tasks but a master of none.
Like kindred Celtic spirits, such as Simon Zebo and Ian Madigan, he went to France and enjoyed a two-year stint of unabashed freedom with Perpignan.
Hook, for a short while at least, just wanted to play the game he wanted which, one would like to think, is hardly the worst crime.
"There is definitely room for players like us in the game, Simon and Ian, always eager to try things off the cuff, sometimes it might come off but other times it doesn't. And that's when you get criticised for doing it. But there should be room in the game for players like that, 100 per cent.
"Myself and Gats actually got on okay. We didn't have a great deal of conversation. He picked the players he wanted. I tried to buy into the way he wanted to play the game but it probably didn't help the amount of positions I played.
"Then I really loved my time in Perpignan. Like with Finn Russell and Zebo, playing with the head up."
He's had fun but that will all end this summer but as he ends his sporting life he will re-write it, as a children's book.
Three years ago, he got the idea when he couldn't find a rugby book in England for his son; so he decided to contact an old friend, an author, to pen his own.
Aptly titled 'Chasing a Rugby Dream', the first of two efforts is out this summer and tells the story of Jimmy, a ten-year-old who wonders what it would be like to be a famous rugby star.
It would be a shame to ruin the ending but we can tell you it is a happy one.