Firstly, the 'Magic If'. The magic if is a technique used by directors to see how the actor is able to react when put into a different situation. For example if a fellow cast member faints, the actor must then almost improvise to show what they would do if that change occurred. When using the magic if , there is no deception involved. "If" creates a problem to solve which will lead one naturally to inner and external action. This helps to develop the character and to see the character from a number of different angles. Also it will give the director a good idea of how well the actor is able to improvise.
Another one of his principles, is 'Given Circumstances'. This given circumstance is all the details given in the play. It can also be any details or notes given by the director. For example; stage directions, props, lighting and costume. A reason to understand why this is used is because although a character may make some choices unconsciously, the actor playing the character is aware of these conditions on a conscious level to help him or her deepen their understanding of the motivation behind the character's actions. Stanislavski is said to have been influenced by Charles Darwin. We can already see the link between the two - science. Science is fact and 100% true and Stanislavski's methods were all meant to be realistic and therefore in the audiences eyes, true.
Stanislavski also taught 'Units' 'Objectives' and 'Super Objectives'. Units were his way of 'breaking down' a scene in order to allow the actor to examine the structure and apply those bits important to his character the most, to his/her acting. Objectives and Super Objectives are what lie in these Units. The Objectives being goals both conscious and unconscious and less