There’s a lot of scholarly writing on incorporation, and this is not an attempt to encompass any of it; I just want to emphasize a point that gets overlooked in hasty discussions of the incorporation of constitutional rights to the states, which is being talked about a lot in the wake of Heller.
The theory behind incorporation is that the Amendment requires states to respect certain substantive guarantees provided in the Bill of Rights. For example, although the First Amendment specifies that “Congress shall make no law...abridging the freedom of speech,” it is now recognized that, thanks to the Fourteenth Amendment, states are also barred from making laws that abridge the freedom of speech. Incorporation through that Amendment reverses the rule established in Barron v. Baltimore, 32 U.S. 243 (1833), a case decided decades before the Amendment was enacted and which held that the Bill of Rights only bars the federal government from doing these things.
But incorporation is not simply an opening through which the rights specified in the Bill of Rights can somehow step and be effective against states. There are two reasons for this. The first, brilliantly elaborated by Akhil Amar in The Bill of Rights, is that the Fourteenth Amendment was enacted some eighty years after the Bill of Rights, and by that time, the phrases in the Bill of Rights were understood somewhat differently than when those phrases were first written. When states are required to abide by the Bill of Rights in a Fourteenth Amendment case, then, they are required to abide by the understanding of those rights in 1868, when the Fourteenth Amendment was written, rather than by the understanding of those rights in the 1780s, when those provisions were originally drafted. The Fourteenth Amendment is therefore a lens rather than a window. This observation can have some very important effects, as in the Establishment Clause cases or the Second Amendment, as Amar shows in his book.
The second, related point is more fundamental: the Fourteenth Amendment does not say “states must respect the Bill of Rights.” What it says is that no state shall make or enforce any law that deprives people of the privileges or immunities of citizenship, or that deprives them of their rights without due process of law. It is when we ask what the “privileges or immunities of citizenship” are, or when we ask what “due process of law” is, that we must look to the Bill of Rights (among other things!) to guide our understanding. It is for this reason that some provisions in the Bill of Rights do not literally apply to the states. Incorporation can logically be less precise than the actual language in the Constitution, because states are required only to abide by the “due process of law” and respect the “privileges and immunities of citizenship,” which are only imperfectly delineated in the Bill of Rights.
The question in an incorporation case is not, Is this right in the Bill of Rights; if so, then states must abide by it. Instead, the question is, What is “due process of law”? Must a state do such-and-so in order for its activities to be regarded as the due process of law? If the state of California throws me in jail for expressing my political opinions, it is not that the court says “well, the First Amendment refers to freedom of speech, and the Fourteenth Amendment applies that to the states, therefore the state’s action violates the Fourteenth Amendment.” Instead, the court says “to throw someone in jail for expressing his opinions is to deprive him of liberty without due process of law, and we know this because the term ‘law’ includes certain substantive protections in the American constitutional order, including the traditional protection of freedom of speech.”
Incorporation, therefore, is not an exact one-to-one ordering of state and federal law; it is an inquiry into whether the state’s action so exceeds the standards of “lawfulness” as to violate the due process of law clause—or whether it deprives a person of the privileges or immunities of citizenship—and that inquiry is guided by reference to the Bill of Rights, among other things, which lay out the standards for determining what constitutes “due process of law.”
(To understand things this way makes clear that incorporation is really not conceptually distinguishable from what is today derided as “substantive due process.” All due process is substantive. So-called “procedural” due process is only a sub-set of substantive due process.)
The first “incorporation” case is Chicago, B. & Q.R. Co. v. City of Chicago, 166 U.S. 226 (1897). But if you look at that case, you’ll see what I mean. The court sifts through a bunch of legal decisions and treatises to conclude that a long-standing, traditional American requirement of “lawfulness” is that government must compensate people when it takes their property: “a judgment of a state court...whereby private property is taken for the state or under its direction for public use, without compensation made or secured to the owner, is, upon principle and authority, wanting in the due process of law required by the fourteenth amendment....” Id. at 241. The question is not whether the compensation requirement of the Fifth Amendment somehow directly applies to the states. The question is whether the compensation requirement articulated in the Fifth Amendment as well as in other sources is so central to the concept of lawfulness that for the state to ignore it would render its acts unlawful, and therefore would mean that the property owner was losing property without “due process of law.”
Obviously this is in part an inquiry into political philosophy—one big reason why it is disfavored today by a Court that would much rather engage in the mechanical jurisprudence of tit-for-tat incorporation. But a proper understanding of incorporation precludes such simpleminded wertfrei jurisprudence. It requires that justices understand the fundamental principles of lawfulness and then apply those principles (although not necessarily their precise instantiation in the Bill of Rights) against states.
Update: Some follow-up thoughts here.