Gall was right in two points, and dead wrong in two other. When he proposed that the brain
was the organ of the mind, he was covering well known ground, with concepts which were widely accepted by philosophers
and physicians alike, in his time.
In addition, Gall's concept of localization of function in the brain was a novel and bold proposition, and was highly influential at the time, bringing attention to this possibility. It was not based on experimentation or clinical observation, but rather on theoretical considerations. Thus Gall's proposal was not scientifically sound, but it hit the mark somehow.
The third tenet of Gall's theory, which was the concept that the brain sub-organs grew accordingly to the development of the corresponding mental faculty, could be possible, but it was also not based on scientific evidence, and could not be empirically tested at the time. Eventually, it caused a great deal of interest on the relation between brain anatomy, size and weight and mental properties, such as intelligence. Nothing of value was to be proved by many objective experiments, at least at the level of gross (macro) anatomy.
The fourth and last tenet was entirely off the mark. The external landmarks and dimensions of the skull have nothing whatsoever to do with the internal conformation of the brain. This can be easily proven, in the times of computerized scanned tomography, which can render the anatomical relations between the two structures with exquisite detail.
From: "Phrenology,
the History of Brain Localization"
By: Renato M.E. Sabbatini, PhD
In: Brain & Mind,
March 1997.