[Greg, who is an expert on Locke and literally wrote the book on the man, thinks I am including him too readily in a general critique of Enlightenment thought. He suggested we make this a whole-blog discussion, rather than keep it in a corner. Here, then, one of my several protestations that Locke–who was my hero for the twenty years it took me to really find Thomas Aquinas–is really deserving of accolades, but lacking in just exactly those resources that we most need at this cultural moment.  In making the case for the prosecution, I think it is quite urgent that readers heed my learned friend, the counsel for the defense, whose arguments are meritorious indeed.]

[pick up the comment thread here, if you like, after perhaps glancing over this post.]

I think Locke can’t protect us from such a lapse without supplementation.

I do not think Locke necessarily tends toward that lapse, or that we can get there without abandoning some of his key views.

But I do think he is vulnerable to such a lapse, even in some of the best parts of the Essay:

1) on Degrees of Knowledge:

These two, viz. intuition and demonstration, are the degrees of our knowledge; whatever comes short of one of these, with what assurance soever embraced, is but faith or opinion, but not knowledge, at least in all general truths. There is, indeed, another perception of the mind, employed about the particular existence of finite beings without us, which, going beyond bare probability, and yet not reaching perfectly to either of the foregoing degrees of certainty, passes under the name of knowledge.

[ http://oregonstate.edu/instruct/phl302/texts/locke/locke1/Book4a.html#Chapter%20II ]

2) IV.xiv on Judgment is brilliant, but note the troubling preference for perception over assent, here; the clarity and distinctness of perception is to the voluntary and relational act of judgment as light is to twilight.  

3) In his section on Faith and Reason, we find

Faith and reason, what, as contradistinguished. I find every sect, as far as reason will help them, make use of it gladly: and where it fails them, they cry out, It is matter of faith, and above reason. And I do not see how they can argue with any one, or ever convince a gainsayer who makes use of the same plea, without setting down strict boundaries between faith and reason; which ought to be the first point established in all questions where faith has anything to do.

and

Faith, on the other side, is the assent to any proposition, not thus made out by the deductions of reason, but upon the credit of the proposer, as coming from God, in some extraordinary way of communication. This way of discovering truths to men, we call revelation.

and

Traditional revelation may make us know propositions knowable also by reason, but not with the same certainty that reason doth.

and

In propositions therefore contrary to the clear perception of the agreement or disagreement of any of our ideas, it will be in vain to urge them as matters of faith. They cannot move our assent under that or any other title whatsoever. For faith can never convince us of anything that contradicts our knowledge. Because, though faith be founded on the testimony of God (who cannot lie) revealing any proposition to us: yet we cannot have an assurance of the truth of its being a divine revelation greater than our own knowledge.

[ http://oregonstate.edu/instruct/phl302/texts/locke/locke1/Book4b.html#Chapter%20XVIII ]

……..but on all these points he can give us no help in avoiding a Cartesian “clarity and distinctness” regress. What is lacking throughout is a conception of grace that makes “traditional revelation” reliable, “original revelation” communicable, faith reasonable, etc. Without that, “faith” in Locke’s world seems to me to function properly only in the gaps in what is reasonable and knowable, in the twilight; there is no clear sense that (a) graced reason–faithful reason–may well be fitter for reason’s own tasks than natural reason, or (b) the proper function of both faith and reason may well be judged on multiple grounds other than “clarity and distinctness”–such as conduciveness to charity, for example.

Compare Aquinas at

Sacred Scripture, since it has no science above itself, can dispute with one who denies its principles only if the opponent admits some at least of the truths obtained through divine revelation; thus we can argue with heretics from texts in Holy Writ, and against those who deny one article of faith, we can argue from another. If our opponent believes nothing of divine revelation, there is no longer any means of proving the articles of faith by reasoning, but only of answering his objections—if he has any—against faith. Since faith rests upon infallible truth, and since the contrary of a truth can never be demonstrated, it is clear that the arguments brought against faith cannot be demonstrations, but are difficulties that can be answered.

[ http://www.ccel.org/ccel/aquinas/summa.FP_Q1_A8.html ]

We have a more perfect knowledge of God by grace than by natural reason. Which is proved thus. The knowledge which we have by natural reason contains two things: images derived from the sensible objects; and the natural intelligible light, enabling us to abstract from them intelligible conceptions. Now in both of these, human knowledge is assisted by the revelation of grace.

[ http://www.ccel.org/ccel/aquinas/summa.FP_Q12_A13.html ]

re: noetic effects of sin [ http://www.ccel.org/ccel/aquinas/summa.FS_Q74_A5.html ] and [ http://www.ccel.org/ccel/aquinas/summa.FS_Q77_A2.html ]

re: ends of reason and need for faith to accomplish that end,

Hence in order that a man arrive at the perfect vision of heavenly happiness, he must first of all believe God, as a disciple believes the master who is teaching him.

[ http://www.ccel.org/ccel/aquinas/summa.SS_Q2_A3.html ]

and even more to the point, Thomas argues that we need faith even to reason well about the subjects natural reason is competent to teach us: [ http://www.ccel.org/ccel/aquinas/summa.SS_Q2_A4.html ]

…now, I think I can sit down with the Essay and reconstruct from various passages how very far Locke goes toward construing an almost-Thomistic view, actually. But much of that would depend on Locke’s blissful inconsistency, because I am convinced he was a really good thinker who tried to hold others back from the slippery slope they all started out on. And that gives him heroic stature in my mind, even though I think he needs help from Thomas and others to crawl away from the edge.