In Time and Free Will, written as his doctoral thesis, Bergson tries to dispel the arguments against free will. These arguments, he shows, come from a confusion of different ideas of time. Physicists and mathematicians conceive of time as a measurable construct much like the spatial dimensions. But in human experience, life is perceived as a continuous and unmeasurable flow rather than as a succession of marked-off states of consciousness — something that can be measured not quantitatively, but only qualitatively. And because human personalities express themselves in acts that cannot be predicted, Bergson declares free will to be an observable fact.