Question

Hello Rabbi,
Following an argument that came up between me and some friends about whether rabbis can give blessings in the sense of “the righteous decrees and God fulfills,” I went back to look at the case of Jacob and Esau. Isaac blesses Jacob instead of Esau, and after Isaac discovers this, he tells Esau that he cannot bless him again with that same blessing, but instead gives him a different blessing. This raised a few questions for me: what actually is a blessing? What does it mean that Jacob took the blessing? Is it really impossible to bless Esau as well afterward? Is a blessing the ability of someone close to God, whatever exactly that means, to influence reality in a miraculous way? Is it Isaac the father’s foresight regarding his son? Is there בכלל any connection between the meaning of blessing as it appears in Scripture and the meaning that various rabbis attribute to it today?