Hume opens the Enquiry by drawing a distinction between two kinds of philosophical thinking. The first he calls an "easy and obvious philosophy" which serves as a guide for the man of action. Usually written in an elegant and poetic style, this philosophy tries to cultivate our manners by drawing on examples from common life and making us feel the difference between vice and virtue. This philosophy excites the sentiments and leads us to assent to a way of life that we know to be good. Such philosophy--which Hume associates with figures such as Cicero, La Bruyere, and Addison--is generally quite popular and keeps good standing in posterity. It follows from common sense and thus rarely falls into error.
This philosophy is contrasted with the "accurate and abstract philosophy" of the man of reason. Rather than direct our behavior, this philosophy seeks to form our understanding and to uncover the principles that govern our behavior. Rather than rely upon common sense, this philosophy--which Hume associates with figures such as Aristotle, Malebranche, and Locke--proceeds by means of abstract reasoning from the particular to the general. This kind of philosophy has little application once one leaves off philosophical contemplation. Because its reasoning and conclusions often go against common sense, error in this field is not at all uncommon, and as a result it fares rather poorly in posterity and is sometimes rejected altogether.
Common wisdom suggests that this accurate and abstract philosophy is not to be disregarded entirely, but that a good life consists in an appropriate mix of different elements. The philosopher is often looked down upon for being too shut off from the world outside, but those who ignore philosophy entirely are even more despised for their ignorance. We are reasonable beings, and thus aspire to scientific knowledge, but this knowledge is limited. We are also social and active beings, though a purely social life can become tiresome and a life devoted purely to business and action can wear us out. The "easy and obvious" philosophy, then, is often considered an ideal that appropriately combines philosophical reflection with a more active and social life. A life dedicated only to the pursuit of scientific knowledge is usually punished with pensive melancholy, uncertainty, and public disapprobation.
Nonetheless, Hume argues that a careful study of this accurate and abstract philosophy has its virtues. It calls for an exactness and accuracy that can lead to perfection in more practical matters. For instance, the scientific study of anatomy may seem grotesque in itself, but a painter can create beautiful and anatomically precise figures through careful application of its principles. Besides, Hume remarks, on its own, such scientific study is harmless, is good exercise for the mind, and can help bring us to the truth.
The best objection Hume admits against accurate and abstract philosophy is that it is not science, but rather a confused attempt to explain by means of blind prejudice what we do not know. However, Hume notes, this is not a reason to abandon philosophy, but an exhortation to study it more carefully. If we can properly explain the nature and principles that govern human understanding, as Newton has done for the principles that govern planetary orbits, we can reject bad reasoning and proceed more carefully. Though the mental faculties are most present to us, they are very difficult to conceive of precisely and we are still far from uncovering the fundamental principles that we seek. Still, this is only further reason to study them, and while we can often make mistakes through faulty reasoning, this fallibility is hardly just cause to abandon the project altogether.
This first section lays out the framework of Hume's project. He is clearly greatly influenced by the scientific method and empirical philosophy. His stated goal is to do for the mind what Newton has done for matter. Before Newton, we could explain a great deal about planetary orbits and even predict how and where things would move. However, until Newton, we were unable to explain why the planets move as they do. Newton's theory of gravitation gives a clear and simple explanation as to why the planets orbit the sun and why objects on the earth fall toward its center. Hume believes our explanations of human understanding and behavior are in a state similar to that of pre- Newtonian astronomy. We can observe a great deal about how we think and can often reason quite fruitfully, but as yet we have no clear grasp of the principles that underlie our thought and reasoning.
Hume's stated method is scientific, of careful observation and inference from particular instances to general principles. The drive of scientific inquiry is to dig deeper and deeper so as to uncover a very few, very simple principles that govern all the complexities that we observe. Newton's genius gives us three very simple laws that can explain and predict all physical phenomena. Hume wishes to perform a similar feat for human understanding (the word "understanding" is used by Hume to describe most broadly the several faculties of human reason). The hope is that Hume will derive a similarly small and simple number of principles that can explain and predict the processes of human thought. His method will be to proceed from simple observation of how the mind works and how we use it in everyday life, and to infer from his observations increasingly general principles that govern our understanding until he reaches a bedrock of simplicity and clarity.
In this respect, Hume follows very much in the empiricist vein of philosophy and owes a large debt to ##John Locke##. Locke moved against rationalist philosophy, best exemplified by ##Descartes##, which relies heavily upon rational intuition. The empiricist tradition asserts that experience, and not reason, should serve as the basis of philosophical reasoning.
The motivation for Hume's project is made apparent in his complaint that the "accurate and abstract" metaphysics that he is pursuing is frequently looked down upon and disdained. The difficulty and counter-intuitive nature of these inquiries often lead to errors that may seem absurd and prejudicial to future generations. Even today, there is a great deal of debate as to whether there has been any real "progress" in philosophy: we may have refined our discussions and dismissed some bad ideas, but in essence we are still mulling over the same problems that concerned Plato and Aristotle. It would not be unreasonable to suggest that we are no nearer a satisfactory and final answer than the ancient Greeks. Hume hopes that scientific observation can uncover the principles that underlie our reasoning so that we can be more immediately aware of faulty logic and more easily guided along the correct path.
Ever since the scientific revolution of Newton, Galileo, and others, science has been held up as a paradigm of fruitful reasoning. In science, there is a carefully defined methodology that precisely details how we can test a theory and determine whether it is right or wrong. Though it is often difficult to determine the right answer, the scientific method usually prevents us from arriving at answers that are far from the mark. Philosophy lacks any such determinate method, and philosophers are continually taking up conflicting views. For instance, Hume's emphasis on observation goes directly against Descartes' rationalism, which disparages observation in favor of pure reason. Hume hopes that his empiricism will open the way for a carefully defined method that will not allow for such disparity amongst philosophers.
Hume also suggests that his work must be epistemically (epistemic: of, relating to, or involving knowledge; cognitive) prior to the new science that he so lauds. The scientific method is a product of careful reasoning, and is thus subject to the laws of human understanding. While science seems to be in far better shape than philosophy, it too can benefit from his work. In this way, Hume differs from his predecessor, Locke. Locke sees himself as laboring on behalf of the new science, clearing away some of the linguistic rubble that might lead to confusion. While Locke humbly sees himself as simply clearing a path for science, Hume believes that his own work must lay the groundwork upon which science can rest. If he can uncover the precise laws that govern our reasoning and inferences, this should help us draw the right conclusions in our scientific investigations.