ABSTRACT
The conventional description of the moon illusion, that the moon at horizon appears larger than it does at zenith, is no longer a sufficient specification of the phenomenon to be explained (McCready, 1986). To most observers the moon is also closer at horizon; at least they say as much. There is a question whether the reports are to be taken at face value or are cognitive modifications of perception, as is argued by Kaufman and Rock, and by Gogel and Mertz in this volume. Whatever the resolution of the matter, the apparent distance of the moon must be considered an essential aspect of the illusion.
