The "refutation" outlined by Pat Gunning iss not quite as conclusive as he would have it. His argument turns on the desire for precise measurement and for equity across all classes of unearned increments. The imposition of a meaningful differential betwewen improved and unimproved land will accomplish much, without pretending full isolation. And there is a difference between classes of rent. Perhaps all classes other than land rent also require the action of the recipient to put their endowments to work, whereas land value increases independent of that due to population growth. Warren Samuels