The purpose of the Lemon test is to determine when a law has the effect of establishing religion. The test has served as the foundation for many of the Court's post-1971 establishment clause rulings. As articulated by Chief Justice Burger, the test has three parts:
According to separationist scholars Barry Lynn, Marc Stern, and Oliver Thomas, the fact that a law may have a "religious purpose or be motivated by religion does not mean it is unconstitutional as long as it also has a bona fide secular or civic purpose" (The Right to Religious Liberty, p. 3). Similarly, "a law that has a remote or incidental effect of advancing religion is not unconstitutional as long as the effect is not a 'primary' effect" (p. 3). Finally, the Court has allowed some entanglement between church and state, as long as this entanglement is not "excessive" (p. 3). Hence, the Court has built some leeway into the test so as not to invalidate laws that have only remote connections to religious practice. This is not, in other words, the work of a Court that was hostile to religion. On the contrary, Justice Burger, a Nixon appointee, is generally reckoned as a conservative on social issues.
We note also that the Lemon test is squarely grounded on the principles articulated in Everson v. Board of Education. Accomodationist legal scholar Stephen Monsma, for example, notes that Burger's opinion is:
The Lemon test has not escaped criticism. Many scholars (including separationists Leonard Levy and Donald Laycock) have argued that the test is unduly subjective and internally consistent, and it's usefulness has been questioned by a majority of the sitting Justices. Still, as noted by Monsma,
...[the test] has not been formally overruled and the basic principles on which it rests--no-aid- to-religion and the sacred-secular distinction--still form the core of what is the dominant line of reasoning dealing with public funds going to religious nonprofit organizations (p. 33)