Just to stir the pot, and promote a lateral view.
Jhana arises and ceases. It arises when conditions are right. It is not permanent or unchanging.
It is a conditioned state. Therefore treating it like it is a chemical formula, or an equation in physics doesn’t really make sense to me. One needs to treat it like other conditioned states… even if it might be ‘less’ conditioned, and even if it leads to greater insights etc. We also possess beneficial conditioned states as well as negative ones…
My 2 cents worth is to relax about it. To concentrate on putting the right conditions in place (as has been mentioned several times) and to always keep questioning and investigating. I believe that many of the ‘formulas’ presented by different Meditation Masters can all be simultaneously correct, they just describe it from different perspectives. The desire for ever greater specificity regarding the phenomena, seems to me to be going in the wrong direction.
Ultimately the only true test can be, if the states result in greater understanding and less suffering as one progresses along the path, and this, we are in the position of observing for ourselves
Anyway this is the way that I’ve chosen to deal with the issue of ‘not knowing’ and living by the Noble 8 fold path.
And it has led to less suffering