This paper begins by briefly contrasting two main theoretical perspectives, the nativist and inatist theories of second language acquisition. It then shifts focus to Stephen Krashen’s natural approach hypothesis, also known as the monitor model. This paper outlines Krashen’s main hypotheses which constitute the natural approach to second language acquisition. Moreover, the paper analyzes Krashen’s theory in terms of its weaknesses, strengths and addresses some of the obvious pedagogical implications that the model has had in teaching English as a foreign language (EFL) and English as a second language (ESL).