Psychology, a new science

Psychology is a incredibly new science and this can be seen when studying the subject. Every topic follows the same process and I think this is due to the lack of concrete evidence. First one theory is released then a second contradictory theory is released that disproves the original theory and finally after the second theory is disproved a third theory comes out combining the first two theories. Take emotion for example. First we learned about the James-Lange theory which says first something is sensed, then arousal occurs and finally the emotion is felt. After issues were brought up with this theory, we learned about the Cannon-Bard theory which says, after experiencing an event the arousal and emotion are felt simultaneously. Finally we learned about a third theory which combines both of these. The Schachter-Singer theory states that a stimulus is perceived, then an arousal is felt as this arousal is cognitively labeled as an emotion and finally a emotion is experienced. This system gives me as a student a feeling of uncertainty in the information I am learning. How do we know that in 5 years a new theory will not be released disproving everything we have learned in the past?