Perhaps it is unfortunate that, no matter what problems a psychological investigator elects to attempt to discuss, he is almost always confronted by a number of different and often conflicting points of view. The twisting paths revealed by these may one day be found to unite into a broad road, but most of them have as yet been insufficiently explored. Certainly problems in the psychology of temporal perception seem to lie in many different directions, according to the ways in which they are approached. It would be possible, for instance, to take the mass of experimental work, always patient, sometimes brilliant, which has had a fairly continuous history since Czermak, in 1857, building upon Weber's researches into space perception, planned and began to carry out a programme for an investigation of the estimation of short time intervals.