Is the Gemara's list of 3/4 keys that are only in Hash-m's hand exhaustive? There would seem to be others that could've been listed- such as, the key to refuah (healing from illness)? In a general sense, what is the characteristic specific to the items on this list that differentiate them from other instances where Hash-m's hand would seem necessarily operative?
Sruel , Queens, NY
The items mentioned here require Divine intervention because they are so basic to human life that Hash-m does not want to give them to an emissary. The three fundamental aspects of life are children, life itself, and sustenance. These three also include healing, which is a part of life, and is also connected to Techiyas ha'Mesim. The Gemara in Pesachim 68a says that we can strengthen our belief in the Resurrection when we see people recover from illness, deriving this from a verse in Ha'azinu.
In another Gemara (Sanhedrin 113a), we find that the keys are indeed given to an emissary but not all the keys can be given to a human being. Thus, Elisha and Eliyahu indeed received one of the three keys but did not get the second key until the first was returned. This is because Hash-m does not want human beings to intervene too much in the natural processes of the world.
Tosfos (Ta'anis 2b) explains that the Gemara in Ta'anis means that the keys are not given to humans permanently but rather for a limited period. This corresponds with our explanation that Hash-m does not want to totally suspend natural processes.