The aim of behaviorism is to provide a strong scientific status to psychology, rejecting obscure theoretical hypotheses and reformulating mentalistic terms like emotions, mind, thoughts etc.
According to John Watson, psychology should be understood as a natural science and needs to be reformed, following the aftermath of the 19th century epistemological crises.
Psychology as the behaviorist views it is seen as an objective and experimental branch of natural sciences, with the final goal being the prediction and control of behaviour.
Introspectionism sees psychology as an analysis of complex mental states divided into simpler elementary constituents and a reconstruction of complex states, focusing on unobservable elements while physical stimuli are seen as mere means to reach the end (mental state).
Watson believes that the time has come for psychology to detach itself completely from anything related to consciousness and become a discipline founded on the continuity between humans and animals, the concept of adjustment to environment and the processes related to it.
Psychology attempts to formulate principles or laws about the adjustment of individuals to every-day life or uncommon situations and it strives to control human behaviour so that society can adjust.
Psychology should aim at guiding society in modifying the environment to suit human ways of acting and in moulding individuals when the environment can’t be modified.
According to Watson, behind every human act there is the same structure, composed of a reaction/response and a stimulus/situation provided by the external environment; these are theoretical assumptions that have to be accepted in psychology in order to study complex processes.
In behaviorism, the goal of psychology is to predict the response given the stimulus or vice versa, it’s generally about the laws governing stimuli and responses.