Everyone who has gone to school has at some time or another had to study "science," but what is it we learn when we study this subject?  In order to talk about our subject here, it will be useful to acquire some vocabulary.  The better you acquire this vocabulary, the easier you will find it to write about the sorts of issues with which this course is concerned.

The first thing that might come to mind is that we have acquired knowledge of a variety of what we might call  scientific facts, beliefs that we hold about the world on the basis of scientific authority.  Such beliefs would be such as the belief that the Earth is the third planet from the sun, that the sun is a star, many times bigger than the Earth, that it is ninety-three million miles from Earth, etc.  We recognize as well that for the expression of such scientific facts numerical measurmenets, sometimes made with astounding precision, are often essential.  Furthermore, beyond the mathematical language employed for expressing some facts, the sciences have devloped a vast professional terminology of terms to which it is often possible to give very precise meanings.  We could imagine "science" as a collosal encyclopedic compendium  of all such precisely expressed "scientific facts" from astronomy through zoology somehow established by each of the various scientific disciplines.

From this perspective, it is obvious that at least one aspect of "science" refers to the endeavor to provide a "description" of nature is a precise and unambiguous manner.  We will refer to this as science's descriptive function.

Notice that all of these "facts" are not on an equal epistemological footing.  That a particular spider has eight legs can be established more or less uncontroversially by naked eye observation.  That Mt. Everest is 29,035 feet above sea level requires a complex calculation from data gathered by sophisticated technology.  That all metals expand when heated is an inference from many observations.  That the current state of the universe began in a "big bang" approximately 15 billion years ago is an inference from a vast body of complex theories and empirical evidence acquired by sophisticated technology.

Considerations such as these have led to distinguishing between "particular facts," which refer to identified observable individuals and generalizations which refer to all members of a very large or perhaps unlimited class of individuals, certainly all of which have not been observed.  Such generalizations cannot be established directly by observation, but rather are inferred inductively from particular facts.

Another distinction is between those "facts" that refer to phenomena and properties or states of such phenomena that can be directly observed.  Such facts are expressed in what philosophers have traditionally called "observation statements" (also "basic statements" or "protocol sentences").  Unfortunately it is not clear what one means by "directly" observed.  Is this meant to exclude what is observed through instruments, the operations of which be simple and intuitive, like a magnifying glass, or may require considerable theory like the "observation" of some fundamental consituent of nature in a particle accelerator?  It is difficult to specify where one can draw a line here.

Obsservation statements are often referred to as empirical statements, or empirical or observational "evidence" or data.  It is important to recognize that while particlar empirical facts can be known directly by experience, all generalization, even though expreseed in purely observational terms require a inference beyond what is directly observed.

In contrast to observation statments, some of the factual claims science makes in describing nature refer to entities, states, or processes that are by their very nature not observable but are postulated by theories.  Thus we do not observe gravitational or electromagnetic fields, electron spin, or nuclear disintegrations, but through theories which postulate these entities, states, or processes we are able to predict that observational evidence which serves to lead to the acceptance of those theories.  All claims of this nature are called "theoretical statments" and it seems that at least some scientific facts describing nature would be of this kind.

No matter whether a statement is held to be "observational" or "theoretical," in either case it must be expressed in precise unambiguous terms.  For each kind of statement, observational or theoretical, there will be appropriate terms, depending on whether these terms refer to what can or cannot be "observed." Thus the distinction between observational and theoretical statements implies a parallel distinction between observational and theoretical "vocabularies" or "languages."  Much of the historical development of science is concerned with the formulation of such "languages" or "conceptual schemes" or "frameworks" necessary for the precise description of nature.

The distinctions between particular and general and between observational and theoretical statements reflect difference in how these statements can be justified.  Therefore an awareness of these distinctions is essential for following much philosophical discissuion of the justification of scientific theories.  However, that is not to say that these distinctions are unproblematic.  In particular, the observational/theoretical distinction has been the subject of much controversy and would be repudiated by many cntemporary philosophers.  However, relating the history of recent philosophy of science would be virtually impossible without making reference to this (perhaps spurious) distinction.

Although an apprteciation of the fact gathering aspect of science is a necessary first step, the conception of "science" as a encyclopedic compendium of "scientific facts" is too simple minded, for one would hesitate to consider the sheer piling up of "facts" to be the essence of the scientists' task.  Thus on a second, perhaps higher, level we can consider science not so much as the body of "facts" compiled by the sum of all sciences, but as the enterprise which strives to explain why those facts are what they are.  Science aspires to tell us not merely what is the case, but to answer why this is so, and these "answers" are known as "scientific explanations."

Since the Question of Authority asks us why it is rational to accept or believe the claims of science, an answer to why these claims are justified must refer back to scientific "explanations."  If I ask why is it rational to believe that all metals expand when heated, the scientist can provide an explanation of why this phenomenon occurs.  Thus the search for an answer to the Question of Authority takes us to the question of the nature of scientific explanation, or in other words, what makes an explanation "scientific."

It may well be that there are more than one kind of scientific explanations, but it has been an assumption of much past philosophy of science that all scientific expanations must have some characteristics in common in virtue of which they are all "scientific."  While it is recognized that many actual explanations science offers are incomplete and fall short of perfection, philosophers have typically tried to build a model of an "ideal" scientific explanation, which is intended to represent the essential characteristics in an ideal, perfected science.  Unfortunately the nature of such an ideal model of scientific explanation is very controversial, and even the attempt to construct such a model would be questioned by many philosophers today.

Of course an explanation might be proposed and it might satisfy the proper form for an ideal scientific explanation and yet still not be the "correct" explanation.  Thus an understanding of philosophical debates surrounding these issues requires that one distinguishes the question of the nature of scientific explanation, what is an ideal scientific explanation and the attempt to build a model of such, from the related but distinct question of what makes that explanation justified.  Thus in addition to developing models of what a scientific explanation is, philosophers also develop models of how scientific explanations get justified. Although how we answer one will undoubtedly condition how we answer the other, care should be taken not to confuse models of what an explanation is with models of how that explanation is justified.

While it is philosophers of science who are concerned professionally with the issues of the nature of scientific justification, it is of course not philosophers, but scientists themselves who actually justify the explanations they propose.  Thus one might suppose that one could discern from what (at least good) scientists appeal to in justifying proposed explanations how scientific explanations are in fact justified.  Here one might sense that there is some agreement, for it is common to find virtually all scientists as appealing to "The Scientific Method" as that which justifies their claims.  Indeed, science education might be thought of not so much as the acquisition of knowledge of scientific facts or explanations, as much as the acquisition of a method by which these claims first discovered and then are justified as rational to accept or believe.

The turn of attention towards method however still leaves the philosopher's question of authority unanswered.  When one gets beyond the level of glib generalizations, it becomes difficult to discern precisely what this "method" is, but even if one could get very clear on precisely what the alleged "sceintific method" is, that would still not show us why believe arrived at as a result of employing this method are ones which any rational person ought to accept.

Again, just as in the case with "scientific explantions," it is by no means clear that there is one and only one "Scientific Method" common to all scientific disciplines.  Indeed the different subject matters of all the different sciences are so varied it is obvious that they will in fact employ different techniques and approaches to the justification of claims within each field.  That all these techniques can be seen as exemplifying some common core underlying method universal to all science is to say the very least quite controversial, if not downright implausible.  Furthermore, attempts to discern some common methodological thread running through the history of science have proved equally frustrating.

At the heart of the philosopher's traditional analysis of scientific methodology lies the endeavor to formulate a "logic of scientific justification" to show how the sorts of evidence appealed to as part of scientific methodlogy, really do warrant, at least a probable inference to the truth of the explanations proposed as a result of the application of this method.

Unfortunately, like many philosophical quests, the hunt for this "logic" underlying scientific methodology has proved baffling.  That there even is such a "logic" is itself an outgrowth of the belief that scientific explanations are indeed justified that has been held by most philosophers of science.  However for science critics, the philosopher's failure to  provide a clear defensible analysis of this alleged logic has led some to hold that the fact that talk of "The Scientific Method" looms so large in science pedagogy and popular writings on science suggests that this appeal may serve as much a rhetorical function persuading us to accept the conclusions of science as it does logical.

So merely to say one ought to accept the "facts of science" because they are the consequences of "scientific explanations," and these explanations are justified as the correct explanations because they have bewen arrived at by application of the "sceintifc method" would not answer the Question of Authority, for we would still be in the dark as to why this method, whatever it might be, rather than for example reading tea leaves or the entrails of sacrificial birds, is the proper method for justifying the beliefs about the world which a rational person ought to hold,