Doctrines, then, are not arbitrary but natural, not accidental but essential.  They are the hypotheses regarding the eternal nature of things drawn from the data of our moral and spiritual experience.  They are to religion just what the science of electricity is to a trolley car, or what the formula of evolution is to natural science, or what the doctrine of the conservation of energy is, or was, to physics.  Doctrines are signposts; they are placards, index fingers, notices summing up and commending the proved essences of religious experience.  Two things are always true of sound doctrine.  First:  it is not considered to have primary value; its worth is in the experience to which it witnesses.  Second:  it is not fixed but flexible and progressive.  Someone has railed at theology, defining it as the history of discarded errors.  That is a truth and a great compliment and the definition holds good of the record of any other science.

Now, if doctrines are signposts, dogmas are old and now misleading milestones.  For what is a dogma?  It may be one of two things.  Usually it is a doctrine that has forgotten that it ever had a history; a formula which once had authority because it was a genuine interpretation of experience but which now is so outmoded in fashion of thought, or so maladjusted to our present scale of values, as to be no longer clearly related to experience and is therefore accepted merely on command, or on the prestige of its antiquity.  Or it may be a doctrine promulgated ex cathedra, not because religious experience produced it, but because ecclesiastical expediencies demand it.  Thus, to illustrate the first sort of dogma, there was once a doctrine of the Virgin Birth.  Men found, as they still do, both God and man in Jesus; they discovered when they followed Him their own real humanity and true divinity.  They tried to explain and formalize the experience and made a doctrine which, for the circle of ideas and the extent of the factual knowledge of the times, was both reasonable and valuable.  The experience still remains, but the doctrine is no longer psychologically or biologically credible.  It no longer offers a tenable explanation; it is not a valuable or illuminating interpretation.  Hence if we hold it at all today, it is either for sentiment or for the sake of mere tradition, namely, for reasons other than its intellectual usefulness or its inherent intelligibility.  So held it passes over from doctrine into dogma.  Or take, as an example of the second sort, the dogma of the Immaculate Conception, promulgated by Pius IX in the year 1854, and designed to strengthen the prestige of the Papal See among the Catholic powers of Europe and to prolong its hold upon its temporal possessions.  De Cesare describes the promulgation of the dogma as follows: