This creates an osmotic pressure gradient that helps to draw water to greater heights. The theory assumes bulk liquid phase behavior in the droplet. The small number of molecules in droplets of 1nm or less in radius makes this assumption dubious. Hence small droplets should evaporate and recondense on the larger ones. Explain why in fact fog does form.
Small droplets are in a metastable state where they tend to spontaneously evaporate.
We need a mechanism for them to form that avoids this problem. Two possibilities exist. It is possible, not not likely that a sufficiently large number of molecules spontaneously condense to form a relatively large droplet. More likely is that small particles of dust act as nuclei for condensation to occur in a heterogeneous manner.