While protoscience is often speculative, it is to be distinguished from pseudoscience and pathological science by its adherence to the scientific method and standard practices of good science, most notably a willingness to be disproven by new evidence (if and when it appears), or supplanted by a more-predictive theory.
Fields such as astrology and alchemy prior to the invention of the scientific method can also be regarded as protosciences. With the advent of the scientific method, they rapidly produced the scientific fields of astronomy and chemistry respectively, leaving those who refused to adopt the scientific method to practice pseudoscience.
Most typically a protoscientific field is one where the hypothesis presented is in accordance with the known evidence at that time, and a body of associated predictions have been made, but the predictions have not yet been tested.
Some protosciences go on to become an accepted part of mainstream science. Others fail to become established, or become pseudoscientific, as their followers persist in the face of lack of scientific evidence for their views.
The most famous modern example of protosciences might be the theory of continental drift as originally proposed by Alfred Wegener (which eventually became an accepted scientific model when the mechanisms of plate tectonics became understood). Other examples include:
Examples of protosciences
Such fields as acupuncture and lucid dreaming can also be categorized as protosciences, pending more evidence and theoretical underpinning.
Other fields, like parapsychology are nearer the boundary between protoscience and pseudoscience.