cific serum and vaccine treatment of certain diseases, of prophylactic measures, and of the specific methods of diagnosis.
The tremendous and revolutionary advance made by medicine in the past few decades is obvious to the most superficial view. It is quite apparent that internal medicine has just been having its Renaissance, even within the lifetime of men now living having passed through that stage of development that other departments of human thought and activity passed through centuries ago. We have only just emerged from the middle ages in medicine. The movement is still in unabated activity. The final goal is far from having yet been reached, and there are vast fields in medicine yet to be cultivated before the one-sided and partial developments of the past will be amplified into a more symmetrical and perfect form. With medical research and progress continuing at the present rate, the outlook is rich with promise for the future development of medicine and added benefits for mankind.
In looking over its history we can distinguish the operation of two contrary tendencies or methods of thought which have controlled the evolution of medicine. These two principles mark off the history of medicine into two epochs, the speculative and the scientific, of a distinctiveness more fundamental than the ordinary division into such periods as the ancient, Arabian and medieval. These two factors are: (1) the subjective, deductive, a priori or speculative, and (2) the objective, inductive, a posteriori, empirical or scientific, methods of attaining knowledge.
The subjective or speculative method is the one that prevailed throughout medical history down to the modern era. It is far the more attractive and has much the stronger hold on human nature; it is the primitive and natural method of the untrained mind. It is easy and pleasant to construct complete schemes of the universe by introspection. Scientific investigation is tedious and laborious, and leaves many gaps in knowledge. There is a demand in human nature for certainty, and completeness, and finality in knowledge. Our patients, for example, demand this in our diagnoses and prognoses. The mind is impatient with the unknown, and is prone to fill up the blanks in knowledge by premature generalizations and assumptions.
The objective or empirical method of gaining knowledge is the one that characterizes modern science. Rigidly suppressing preconceived notions and bias, this method proceeds by painstaking observation and investigation to collect an adequate mass of objective data as a prerequisite to generalization. This method is not natural to human nature, but is a product of culture. In the history of mankind, it was ages before, in the Renaissance, it came to dominate the best thought; and among the mass of people at the present time it is only a cultured few who are thoroughly imbued with its spirit.