Understanding leads to certainty, much like faith.
Certainty removes the need to think things through, to decide, to judge, to have an opinion.
When thinking ceases, the mind moves out of the way and reveals the NOW, which is either observed or experienced or both. The NOW cannot be thought, thinking invokes PAST and FUTURE. Put another way, thinking manifests space-time, which is Not-Now!
So, we use the thinking process to understand something, so that we can remove the thinking process from the equation and reveal a witnessing/feeling of the present moment.