Remember that Serial Dilution technique you learned in high school chemistry? You mix one part base with nine parts solvent, and then use that solution as the base to which you add nine parts solvent, and so continue as long as you wish. Each step results in a ten-fold reduction in the concentration. You start out with, say, raw battery acid, and after five or six steps you could drink the solution on the rocks with no ill effects.
What brought serial dilution to mind was a number of recent articles in which Catholics are invited to embrace "a diversity of religious perspectives" about teachings that belong to the deposit of faith.
Here's what's going on: doctrinal differences are reductively treated as theological differences, which are in turn reductively treated as methodological differences, which are reductively treated as aesthetic preferences, i.e., matters of taste.
Take the example of two mass-goers. One believes that, through Christ's action in the priest-celebrant, the wheaten host is changed in the Eucharist such that Christ is really present under the appearance of bread. Another mass-goer believes that the Eucharistic ceremony changes not the host but rather the dispositions of the recipient, and that a rice-flour wafer would serve the purpose just as well.
In traditional terms, this disagreement would be called a difference of doctrine, and their contradictory convictions would in and of themselves put the disputants in different Churches (in the 16th and 17th centuries, differences of this scale provided the grounds for wars of religion). Dilutors, however, treat the disagreement in the first instance as a difference not in doctrine but in theology: the former mass-goer has a Thomistic theology employing the concepts of substance, act, &c., the latter a process theology that explores the developing subjectivity of the observer. In the next step, these theological differences are explained as divergent methodologies, the former being "static" and aimed at cognitive clarity, the latter being "dynamic" and oriented toward a plurality of associative responses. These methodologies, finally, are placed beyond the sphere of rational choice -- and therefore beyond criticism and justification -- but are seen to be "pre-discursive" preferences. One man just prefers Bach to Debussy; another just prefers Debussy to Bach. One man just likes peace ice cream more than chocolate; another just likes chocolate ice cream more than peach. One man just happens to believe in the Real Presence; the guy in the next pew just happens to disbelieve it. "So why," the dilutors ask, "do you get flustered and angry about questions of taste? Let's celebrate diversity." Not only has orthodox teaching on the Eucharist been gutted of any force, but the doctrine of doctrine has disappeared.
"There are many gifts," says St. Paul, "but the same Spirit." Paul might be called the apostle of diversity. "Are all prophets?" he asks, " Are all teachers? Do all work miracles?" He wants the Corinthians to stop bickering about the relative importance of their roles and rejoice in the variety of gifts. But the reason for the variety is to preach an invariant body of doctrine. And regarding that body Paul had zero tolerance for diversity, as we read in Galatians 1:9: "As we have said before, so now I say again, If any one is preaching to you a gospel contrary to that which you received, let him be anathema." Not, let him share the pulpit with an orthodox Catholic on alternate weekends; let him be excommunicated.
It's not impossible that the homily you heard this Sunday was an example of doctrinal dilution. If it was, ask yourself: was it in any sense Good News? Is there anyone, in any circumstances, alive in any epoch, for whom it could be?