In Book VI of the Nicomachean Ethics Aristotle makes the assumption that there are five states of the soul through which we interact with truth. He continues Book VI with a discussion of his intended meaning of each of these states of the soul. In this study the relevant discussions on each state are extracted from the text to enable a clearer understanding of these states, as Aristotle presents them. Subsequently, the role of each state is studied in the context of the entire Nicomachean Ethics. The primary focus is directed at a clearer understanding of Aristotle’s proposed intellectual virtues, and on their respective roles in the ethical life. Simultaneously, the ethical life that Aristotle presents, and its ultimate end eudaimonia, or happiness, are approached from this perspective. Aristotle argues that reason is the distinguishing feature of humans, and that man’s excellence must include the excellent use of this capacity. This study investigates how Aristotle proposes that the rational intellect should reach its completion, and comes to the conclusion that true mastery of the intellect can only result from the cooperation of the five states of the rational soul. It becomes evident that each state of the soul has a different nature and function, and that through directed cooperation they do not compete with one another, but are mutually enhanced. However, Aristotle repeatedly emphasises the importance of extending thought into action. This makes Aristotle’s ethical theory so attractive: he manages to consolidate his theorizing with the value of experienced reality. This is his essential key to happiness, which is experienced both in perception and in action. By approaching the Nicomachean Ethics from the perspective of the five states of the rational soul, an appreciation is acquired for the fine balance by which action and reason may combine to result in man’s fulfilment of his highest potential. It is in this balance that one finds the secret to eudaimonia.