A case is made that in the absence of an effective feedback control on the rate of delivery of CaO to the oceans, the CO2 content of the Earth's atmosphere would have wandered over a large range threatening life either by overheating or by carbon dioxide starvation. In this paper, we defend the suggestion by Walker et al. [1981] that control is exerted by the interaction between the CO2 content of the atmosphere and the continental weathering rates. We contend that in spite of the arguments raised against it [Raymo and Ruddiman, 1992; Edmond and Huh, 1997] the CO2- chemical weathering feedback is the dominant mechanism that stabilizes the atmospheric carbon dioxide content. ¿ 1998 American Geophysical Union