"No one can be a true mystic who is not thoroughly versed in the ways of nature. The more nature is attracted by spiritual favors, the more it is inclined to make itself the master of them. Nature always mingles its own spirit with the spirit of God. unless we keep a close watch over it, it will always remain so. Natures most subtle snare is to lead us to confuse what is licit with what is expedient. When we doubt the inspiration of an impulse, whether from grace or nature, we should picture a similar object which is without doubt acceptable to nature. If this representation pleases us, it is a sign that the first inclination also comes from nature and is consequently to be rejected."