One of the most useful things I’ve learnt over the years is to remember that if you don’t know what is going to happen, don’t structure your portfolio as though you do!
This is why things like asset allocation, a properly diversified portfolio and discipline are so important to long term success where success is defined by having enough when you need it.
The full post (it is a long one) explores what Montier says is now and will continue to be a low return world. He uses math to lay out where a 60/40 portfolio will annualize between 0.70% and 1.70% in real returns for the next seven years. He also talks about his belief in reversion to the mean and how that will play into things in the current central bank influenced world and the risk inherent in chasing yield.
To the quote above, everyone has opinions on what will happen but of course no one can actually no. In this context there is a difference between tilting to an expected outcome and selling out totally at the expense of remaining diversified and generally sticking to a strategy.
There is a lot of good stuff in there even if you don't agree with everything he says--I don't agree with him on everything in there.