Spiritual color blindness

From Holiness by J.C. Ryle, Chapter 19 Wants of the Times:

I cannot withhold my conviction that the professing church is as much damaged by laxity and indistinctness about matters of doctrine within, as it is by skeptics and unbelievers without. Myriads of professing Christians nowadays seem utterly unable to distinguish things that differ. Like people afflicted with color blindness, they are incapable of discerning what is true and what is false, what is sound and what is unsound. If a preacher of religion is only clever and eloquent and earnest, they appear to think he is all right, however strange and heterogeneous his sermons may be. They are destitute of spiritual sense, apparently, and cannot detect error. Popery or Protestantism, an atonement or no atonement, a personal Holy Spirit or no Holy Spirit, future punishment or no future punishment, "high" church or "low" church or "broad" church, Trinitarianism, Arianism, or Unitarianism, nothing comes amiss to them: they can swallow all, if they cannot digest it! Carried away by a fancied liberality and charity, they seem to think everybody is right and nobody is wrong, every clergyman is sound and none are unsound, everybody is going to be saved and nobody is going to be lost. Their religion is made up of negatives; and the only positive thing about them is, that they dislike distinctness, and think all extreme and decided and positive views are very naughty and very wrong! ...

For your own soul’s sake dare to make up your mind what you believe, and dare to have positive distinct views of truth and error. Never, never be afraid to hold decided doctrinal opinions; and let no fear of man and no morbid dread of being thought party–spirited, narrow or controversial, make you rest contented with a bloodless, boneless, tasteless, colorless, lukewarm, undogmatic Christianity.