The energetics of the mechanism of saponification were previously under debate, but I will admit, I misrepresented a point.
Here is the revised mechanism of saponification proposed by someone other than myself. It is the one on top.
The previously suggested mechanism is in the middle.
The textbook mechanism is the bottom one.
Now, it does seem that if the mechanism were concerted then proton abstraction would be much more plausible from a thermodynamic standpoint. If the second mechanism were akin to scaling Mt. Everest, then the first one looks to me to be more like climbing the rock wall at the gym.
We start with the same reactant - an ester - but in the second mechanism we are going through a dianion intermediate. In the first mechanism however we are simply going through a concerted transition state en route to the stable carboxylate.
So, again, I ask - which is (kinetically) correct?