Lee Strasberg was an actor who believed that the work of the actor involved two areas. These areas were the ability to create and express reality. In order to create reality, you would have to think of sad or happy memories from the past to act out the emotions. This would make it realistic instead of overexagerated. Additionally, it would give the play more emotions. The other area it to express reality. This involved acting in the moment and thinking on your feet. You don't need to follow every word of the script. If something unexpected happens then you would need to act on your feet. This is how Lee Strasberg thought acting should be done.