In the scholarly literature, John Locke (1632–1704) features as a formative influence on Newman’s philosophical thought. What usually gets highlighted, for example in the Essay in Aid of a Grammar of Assent, are Newman’s criticism of Locke’s notion of degreed assent and his call for a broader and more nuanced account of the rationality of religious belief. However, some have argued that the Grammar largely focuses on the psychological conditions of religious belief. C. Stephen Dessain, for example, claims that it is a “common misconception” to think of the Grammar as a “philosophical treatise.” One thing, for Dessain, that is “clear, and it cuts the ground from under a host of criticisms,” is namely, that “Newman is not dealing with the problem of epistemology.” Instead, Newman frames and addresses the relevant problems in “psychological” (not in epistemological) terms. Thus, the Grammar is not exploring religious knowledge but only how our minds happen to work regardless of whether religious belief is rational.
However, we think it is a mistake to restrict the focus of the Grammar to the psychology of religious belief. We contend that while Newman homes in on how the mind actually works and on the rational status of religious belief, a central theme in the second part of the Grammar is certitude in an epistemic, rather than merely a psychological, sense. This is perhaps most clearly seen when Newman challenges the claim of Locke and his followers that knowledge is restricted to intuition and demonstration. As Kenny Pearce points out, Locke’s “whole Essay is characterized by a modest, if not skeptical, epistemology and has as one of its key conclusions the denial that genuine knowledge is to be had in revealed religion.” In the chapter on faith and reason, for example, Locke applies his epistemological principles to religious belief. He seeks to clarify the distinction between the distinct provinces of faith and reason; conflating them, he adds, has been the “cause, if not of great Disorders, yet at least of great Disputes, and perhaps mistakes in the World.” He concludes that faith, and the relevant appeal to divine revelation, falls short of knowledge. “And herein lies the difference between Probability and Certainty, Faith and Knowledge, that in all the parts of Knowledge, there is intuition, each immediate Idea, each step has as its visible and certain connexion; in belief not so.”
Newman’s engagement with Locke in the Grammar is both appreciative and critical. As Basil Mitchell points out, Locke’s “careful and sympathetic attempt to delimit the spheres of reason and revelation, while leaving the final judgement with reason, was felt by Newman to be profoundly unsatisfactory, albeit never to be dismissed out of hand.” On the one hand, Newman deeply admires Locke’s commitment to the pursuit of truth. He concurs with many of Locke’s “remarks upon reasoning and proof” and with his critical evaluation of enthusiasm. On the other hand, undergirding Newman’s critical engagement with Locke is the claim that we should let the empirical facts guide our epistemological categories. Locke, according to Newman, proceeds more from an a priori view of human cognition than from the world of “facts”—a stinging critique of the father of British empiricism. More precisely, Newman’s appeal is to the natural “constitution of the human mind as we find it,” and not to how we think it ought to work. This emphasis on how our minds actually work is what has led many to think he is simply interested in psychology. Yet, Newman observes human nature to help determine the bounds of human knowledge itself. Others, seeing Newman’s critique of Locke, recognize that Newman’s project is epistemological but then conclude that he proffers a quasi-fideism or an anti-evidentialist position in epistemology. However, Newman is not rejecting Locke’s evidentialist epistemology per se but rather challenging him on the nature and scope of knowledge and certitude.
As indicated, a key issue (and perhaps the key issue) in the second part of the Grammar is whether probable reasoning can lead to certitude. This gives us yet another indication that Newman’s project is epistemic, for knowledge and certitude are tightly connected concepts for both Newman and Locke. Yet, Locke holds that beliefs based on probabilities cannot achieve certitude, and so do not constitute knowledge. In other words, “Absolute assent has no legitimate exercise, except as ratifying acts of intuition or demonstration.” Anything that falls short of these acts is “but Faith, or Opinion, but not knowledge.” On this point, Newman disagrees. He rejects the “pretentious axiom that probable reasoning can never lead to certitude.” Newman not only seeks to show that there can be appropriate certitude, and even knowledge, in matters of religion but also in other aspects of life. There are many propositions to which we unconditionally assent, though they do not arise from demonstration or intuition.
As we have seen, Locke thinks that religious certainty is impossible for those who adhere to religious faith. The same seems to be the case in Newman’s correspondence with William Froude. Froude seemed to think that certainty could be secured if and only if one had perfect evidence that was exempt from all possible doubt. Certainty, for Locke, is an epistemic state. It is built “upon the clear Perception of the Agreement, or Disagreement of our Ideas attained either by immediate intuition” or in “demonstration.” Beliefs based on probabilities fall short of certainty.
Newman likewise thinks that certitude is an epistemic state, not merely a psychological feeling. He defines it as the “perception of a truth with the perception that it is a truth, or the consciousness of knowing, as expressed in the phrase, ‘I know that I know,’ or ‘I know that I know that I know,’-or simply ‘I know’; for one reflex assertion of the mind about self sums up the series of self-consciousnesses without the need of any actual evolution of them.” The disagreement, then, is not over whether certitude is an ingredient or component of knowledge (or reflective knowledge) but over the epistemic scope of certitude. Locke, as we have seen, thinks that probability falls short of knowledge. As he says, “Probability, then, being to supply the defect of our Knowledge, and to guide us where that fails, is always conversant about Propositions, whereof we have no certainty, but only some inducement to receive them for true.” Newman, by contrast, holds that certitude can arise via probabilistic evidence rather than strict demonstration or rational intuition.
In this respect, Newman targets Locke’s chapter in the Essay concerning Human Understanding that distinguishes knowledge (and certitude) from probability. Locke acknowledges that “most of the Propositions we think, reason, discourse, nay act upon, are such, as we cannot have undoubted Knowledge of their Truth; yet some of them border so near upon Certainty, that we make no doubt at all about them; but assent to them as firmly, and act, according to that Assent, as resolutely, as if they were infallibly demonstrated, and that our Knowledge of them was perfect and certain.” In effect, Locke, according to Newman, “affirms and sanctions the very paradox” to which Newman himself is “committed.” And so it would be easy to see why Newman draws attention to the exceptions that Locke makes in his treatment of knowledge (those things that are so close to certain that we can treat them as certain and therefore as knowledge).
Locke’s admission that humans naturally treat propositions as certain even though they are not the product of rational intuition or strict demonstration only shows that his standard for knowledge and certitude is too restrictive. He circumscribes the realm of knowledge and certitude in a way that does not fit the “common voice” of humanity; for we are often certain on less than conclusive evidence. The non-demonstrative conclusions to which we assent with certitude are “numberless” rather than few. For, “It is a law of nature then, that we are certain on premises which do not touch [reach] demonstration.” Newman adds, “If our nature has any constitution, any laws, one of them is this absolute reception of propositions as true, which lie outside the narrow range of conclusions to which logic, formal or virtual, is tethered; nor has any philosophical theory the power to force on us a rule which will not work for a day.” For Newman, the real contrast is between demonstrative and non-demonstrative ways of acquiring certitude, not, as Locke stipulates, between certitude and probability.
As a result, Newman’s engagement with Locke is not restricted to an exploration of human psychology. Newman’s struggle with Locke is over whether there can be religious knowledge. Knowledge (and certitude), as Newman seeks to show, has a “natural,” “normal,” and “legitimate place in our mental constitution.” Newman agrees with Locke that a “lover of truth” should not hold “any proposition with greater assurance than the proofs it is built upon will warrant.” Yet, there are assents that people give on “evidence short of intuition and demonstration, yet which are as unconditional as if they had that highest evidence.” Newman broadens Locke’s category of knowledge by allowing beliefs that have nearly conclusive probabilistic grounds. After all, Newman argues, we know (on probabilistic grounds)—and are even certain—that we will die, that there is an external world, and that Great Britain is an island. Such beliefs receive unqualified acceptance, though they they cannot be demonstrated. On “all these truths we have an immediate and an unhesitating hold, nor do we think ourselves guilty of not loving truth for truth's sake, because we cannot reach them through a series of intuitive propositions.” People render unconditional assents to propositions that fall short of demonstrative proof and admit of nothing higher than probable reasoning.
As M. Jamie Ferreira points out, Newman’s preferred model is cumulative or convergent reasoning in which the resultant certainty is “constituted by the absence of reasonable doubt,” and it is “more than simply the assurance for practical needs.” Convergence, for Newman, is an ordered collection of concrete instances with the special quality of strengthening one another. He illustrates this reasoning process with the example of a cable. A cable is composed of several strands; individually each is weak and insufficient to support a belief, but collectively they are as “sufficient as an iron rod” (e.g., mathematical or strict demonstration). The cable symbolizes “moral demonstration, which is an assemblage of probabilities, separately insufficient for certainty, but, when put together, irrefragable.” People who refuse to depend on the durability of a cable and demand “an iron bar, would, in certain given cases, be irrational and unreasonable.” The same applies to people who say that a religious belief is rationally acceptable if and only if that belief can be supported by “rigid demonstration,” rather than by “moral demonstration.”
If the foregoing has been correct, the Grammar does not merely focus on the psychological conditions of religious belief. Newman’s project is philosophical; he explores the epistemic nature of certitude. Moreover, Newman’s philosophical disagreement with Locke is not even over the rational status of religious beliefs rooted in a cumulation of probabilities. Locke grants the rationality of such beliefs. Newman’s genius was to expand the epistemic realm of certitude beyond what Locke in principle acknowledges but in fact does not allow. Newman insists that the cumulation of probabilities can lead to certitude, and this certitude is not just rational or reasonable but can constitute knowledge. His proposal leaves us with the sense that his categories of certitude and knowledge are much broader than Locke’s and more in keeping with the actual human experience of knowledge and certitude.
 See Basil Mitchell, “Newman as a Philosopher,” in Newman after a Hundred Years, eds. Ian T. Ker and Alan G. Hill (Oxford: Clarendon Press, 1990), 223; James Collins, ed., Philosophical Readings in Cardinal Newman (Chicago: Henry Regnery Company, 1961), 9–10; J. M. Cameron, “Newman and Locke: A Note on Some Themes in An Essay in Aid of a Grammar of Assent,” Newman-Studien 9 (1974): 197–205; R. A. Naulty, “Newman’s Dispute with Locke,” The Journal of the History of Philosophy 11 (1973): 453–77. Martin Cyril D’Arcy, The Nature of Belief (Westport, CT: Greenwood Press, 1931), esp. ch. 5; William Fey, Faith and Doubt: The Unfolding of Newman’s Thought on Certainty (Shepherdstown, WV: Patmos Press, 1976), 72–76; M. Jamie Ferreira, Scepticism and Reasonable Doubt: The British Naturalist Tradition in Wilkins, Hume, Reid and Newman (Oxford: Clarendon Press, 1986); Frederick D. Aquino, “The British Naturalist Tradition,” in The Oxford Handbook of John Henry Newman, ed. Frederick D. Aquino and Benjamin J. King (Oxford: Oxford University Press, 2018), 154–72; and Becky Walker, “The Lockean Influence on Newman’s Epistemology: An Historical Analysis Describing Newman’s Engagement with Locke’s Ideas,” Irish Theological Quarterly 84, no. 1 (2019): 77–91.
 See, for example, Basil Mitchell, “Newman as a Philosopher,” 223; Frederick D. Aquino, Communities of Informed Judgement: Newman’s Illative Sense and Accounts of Rationality (Washington DC: Catholic University of America Press, 2004); David Pailin, The Way to Faith: An Examination of Newman's Grammar of Assent as a Response to the Search for Certainty in Faith (London: Epworth Press, 1969), 187; Jay Newman, The Mental Philosophy of John Henry Newman (Waterloo: Wilfrid Laurier University Press, 1986), 26–27.
 C. Stephen Dessain, “Cardinal Newman on The Theory and Practice of Knowledge: The Purpose of the Grammar of Assent,” Downside Review 75, no. 239 (1957): 7. See also John Hick, Faith and Knowledge, 2nd edn. (London: Macmillan Press, 1988), esp. ch. 4; Zeno, “An Introduction to Newman’s Grammar of Assent,” Irish Ecclesiastical Record 103 (1965): 389–406; and Cameron, “Newman and Locke,” 197–205.
 Dessain, “Cardinal Newman on the Theory and Practice of Knowledge,” 16.
 N. D. O’Donoghue, “Newman and the Problem of Privileged Access to Truth,” Irish Theological Quarterly 42 (1975): 258, likewise says, “the Grammar stands and will stand, always powerful and persuasive as a personal statement, penetrating as a psychological exploration of the mind in search of certainty.” Yet it “fails” as “a systematic treatise,” especially since it does not succeed in offering the relevant “proof of Christianity” and does not possess “the hardness of texture demanded by a theory of certitude.” The appeal to the illative sense, for instance, does not bridge the gap between probability and certainty. Instead, “what bridges the gap in the Grammar is a persuasive and self-persuasive rhetoric.”
 See John R. T. Lamont, “Newman on Faith and Rationality,” International Journal for Philosophy of Religion 40, no. 2 (1996), 63–84.
 Kenneth L. Pearce, “Berkeley’s Lockean Religious Epistemology,” Journal of the History of Ideas 75, no. 3 (2014): 417. As Michael Ayers, Locke: Epistemology and Ontology (London/New York: Routledge, 1996), 121, points out, Locke’s “evident purpose in the chapters ‘Of Faith and Reason’ and ‘Of Enthusiasm’ was to clip the wings of revelation by subordinating it to ‘reason,’ i.e. to the natural faculties in general.”
 John Locke, An Essay Concerning Human Understanding, ed. Peter H. Nidditch (Oxford: Clarendon Press, 1975), 4.18.1; henceforth cited as ES.
 Locke, ES, 4.15.3; see also 4.18.4–6.
 Mitchell, “Newman as a Philosopher,” 224.
 Newman, GA, ed. Ian T. Ker (Oxford: Clarendon Press, 1985), 107.
 Newman, GA, 106, 142. In a letter to R. H. Hutton in 1870, however, Newman clarifies his criticism of Locke’s notion of the a priori: “I accuse Locke and others of judging of human nature, not from facts, but from a self-created vision of optimism by the rule of ‘what they think it ought to be.’” In fact, Locke’s account “is not from experience, but from pure imagination.” LD xxv, 115..
 E.g., Duncan Pritchard, “Faith and Reason,” Royal Institute of Philosophy Supplement 81 (2017): 113–14.
 Martin Smith, “The Epistemology of Religion,” Analysis Reviews 74, no. 1 (2014): 136, says Newman, like William James, “appears to reject the idea” of evidentialism in the Grammar. Cf. e.g., Duncan Pritchard, “Faith and Reason,” Royal Institute of Philosophy Supplement 81 (2017): 113–14; Cf., Peter Forrest, “The Epistemology of Religion,” Stanford Encyclopedia of Philosophy (https://plato.stanford.edu/entries/religion-epistemology).
 We acknowledge that the relationship between certitude and knowledge in Newman’s thought is complex. On the one hand, he repeatedly defines certitude in the Grammar in terms of knowledge. On the other hand, he seems to make a distinction between mere and reflective knowledge (see GA, 134). So, it is not clear whether certitude is required for both. That said, Newman most definitely has epistemic states like knowledge or understanding (higher, reflective knowledge) in mind when he speaks of certitude.
 Newman, GA, 106. See also Locke, ES, 4.3.6–8, 14; 4.15.1–3.
 Locke, ES, 4.2.14.
 Newman, GA, 106.
 Ferreira, Scepticism and Reasonable Doubt, 230, argues that Newman and Reid “share a criticism of Locke’s methodological refusal to consider as philosophically relevant” what all people “call knowledge or certainty.”
 Locke, ES, 4.18.5.
 Newman, GA, 129; see also 134.
 Locke, ES, 4.15.3.
 Newman clarified his terminology in a letter to J. D. Dalgairns: “This is far from my meaning. I use ‘probable’ in opposition to ‘demonstrative’--and moral certainty is a state of mind, in all cases however produced by probable arguments which admit of more or less--the measure of probability necessary for certainty varying with the individual mind.” LD xi, 289.
 Locke, ES, 4.15.
 Locke, ES, 4.15.2; emphasis ours.
 Newman, GA, 107.
 Newman, GA, 106.
 Newman, GA, 116.
 LD xxiv, 104. See also Naulty, “Newman’s Dispute with Locke,” 455.
 Newman, GA, 118.
 LD xi 289, 293.
 Newman, GA, 137, 149.
 Newman, GA, 108; see Locke, ES, 4.19.1.
 Newman, GA, 116ff.
 Newman, GA, 118.
 Ferreira, Scepticism and Reasonable Doubt, 227.
 LD xxi, 146. See also Newman, GA, 187: “It is the cumulation of probabilities, independent of each other, arising out of the nature and circumstances of the particular case which is under review; probabilities too fine to avail separately, too subtle and circuitous to be convertible into syllogisms, too numerous and various for such conversion, even were they convertible. As a man’s portrait differs from a sketch of him, in having, not merely a continuous outline, but all its details filled in, and shades and colours laid on and harmonized together, such is the multiform and intricate process of ratiocination, necessary for our reaching him as a concrete fact.”
Frederick D. Aquino is Professor of Theology and Philosophy at the Graduate School of Theology, Abilene Christian University (ACU), and the director of the philosophy minor at ACU. His books include Communities of Informed Judgment (CUA, 2004), An Integrative Habit of Mind (NIU, 2012), Receptions of Newman (Oxford, 2015), co-edited with Benjamin J. King, The Oxford Handbook of the Epistemology of Theology (Oxford, 2017), co-edited with William J. Abraham, and The Oxford Handbook of John Henry Newman (Oxford, 2018), co-edited with Benjamin J. King. His research interests include religious epistemology, spiritual perception, John Henry Newman, and Maximus the Confessor. He is currently working on a constructive account of spiritual perception and on the relevance of John Henry Newman for issues in contemporary epistemology.
Logan Paul Gage is Associate Professor and Chair of the Philosophy Department at Franciscan University of Steubenville. He specializes in epistemology and natural theology.