There appear to be times when philosophers use these terms 'sense-data' and 'facts' synonymously, and at other times as distinct entities. Is there philosophy that speaks to characterize the relationship between them? Is there a simple difference between them?

  • 1
    Sense data is something like mental images, facts are what those are of, and they do not have to be directly sense related (if at all). Conservation of energy is a theoretical fact, for example, whatever makes Pythagorean theorem true is a mathematical fact. I doubt that anybody would use them synonymously, except in a loose elliptic way for sense facts.
    – Conifold
    Nov 2, 2020 at 22:12
  • I will disagree with Conifold here. SENSE DATA can Express IN SCIENCE the times we use our famous FIVE SENSES: sight, hearing, taste, smell & touch. This is what ALL SCIENCES must have to be a science in the first place. There are NO SCIENCES that are not physical in some way. Even the word PROOF or PROVE appeals to at least one of the 5 senses. FACT outside of SCIENCE can Express things that are independently true in reality that never change truth value. There is a good chance that is what some philosophers have meant NOT the science definition. Science is about the senses.No ducking this.
    – Logikal
    Nov 3, 2020 at 4:14
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    Great question. Did you have specific examples? Pay particular attention to the notion of brute fact which are facts that seem to derive directly from sense-data. Some philosophers draw distinction between the social process of building facts and facts that seem self-evident.
    – J D
    Nov 8, 2020 at 16:56
  • Facts are valid propositions, propositions are elements of knowledge. But sense-data is information obtained from perception. There is a clear difference: sensing data (e.g. perceiving a lake) does not mean that the existence of the lake is a fact, you are perhaps experiencing a delusion. That is, in essence, what your references state, and they seem correct.
    – RodolfoAP
    Nov 8, 2020 at 16:58
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    Can you give us a case or two of a philosopher using the terms 'sense-data' and 'facts' synonymously? Or maybe the context(s) in which your recall them so used? Or philosophical or scientific contexts in which such a confluence of ostensibly disparate terms is unavoidable given the thesis that is being put forward?
    – gonzo
    Nov 8, 2020 at 17:57

2 Answers 2


I guess it to some extent reduces to where these entities are thought to be "located."

Qualia-like sense data are generally considered to be located In ones mind, in that they are "the alleged mind-dependent objects that we are directly aware of in perception, and that have exactly the properties they appear to have." (See SEP).

Whereas "facts" (ala correspondence theory and its ilk), are something like states of affairs [out there] known (how, and by whom?) to be true, to exist, or what is thought to be the case? As Wittgenstein said in the *Tractatus, trying to dissolve the issue: "The facts in logical space are the world," (1.13). And "The world divides into facts." (1.2)

Nevertheless, strictly speaking, there is the [inferential] leap from the "known" to exist (phenomena-sense data) to what actually exists (noumena-facts). that is, it is only by inferring from one's available "sense data" that one can say whether the something is or is not a "fact."

  • So, it's about the dichotomy of the internal and the external in your view?
    – J D
    Nov 8, 2020 at 16:54
  • @ J D If the complex relationship and distinctions between a 'fact' (as described by Wittgenstein) and a 'sense datum' is to be made "simple", as the OP requires, then I guess my answer to your question would be yes.
    – gonzo
    Nov 8, 2020 at 17:06
  • Thanks. I have been thinking a lot of the notion of the brute fact and your answer seems to suggest that the 'bruteness' is a matter of location. Something to meditate upon, thanks.
    – J D
    Nov 8, 2020 at 17:12
  • @ J D No problemo. BTW Can you offer, as I asked the OP, an case or two of a philosopher using the terms 'sense-data' and 'facts' synonymously." Or maybe conceive of contexts in which they are so used? – Better: contexts in which such confluence of disparate terms would be unavoidable?
    – gonzo
    Nov 8, 2020 at 17:21
  • I'll see if I can't tackle that.
    – J D
    Nov 8, 2020 at 17:30

There has been a request made from a SEP member to see some documentation concerning any author who espouses that 'facts' and 'sense data' are treated as synonymous.

What follows is the full version from which I compacted my latest comment concerning the inherent difficulties with both facts and data as scientifically non-problematic.

This excerpt is from the Prolegomena, pp.24-25, under the heading, (i) Natural Causes Incoherent in Prof. HF Hallett's, "Creation, Emanation and Salvation".

See the bolded segment for the focused response to the member's request.

"Similar difficulties have always haunted the causal theories of empiricist and positivistic thinkers; for spatial contiguity and temporal succession cannot, without the surreptitious or overt introduction of some factor which involves or insinuates agency, be made to yield a relation even seemingly causal. The antecedent and the sequent must, as such, be temporally separate, and thus distinct and disconnected; and however narrow the interval may be taken to be, this disconnection baffles the search for a causal relation of distinct essences. The attempt to avoid this impasse by reducing the temporal gap to the ideal limit of a mathematical section, the antecedent lying on one side, and the sequent on the other, must fail because thus also antecedent and sequent must approximate to identity. The defense of 'natural causation' thus requires what ex hypothesi cannot be allowed, viz. the elimination of the temporal disconnection of antecedent and sequent, the emendation of the pulverulence of time. Nor is this alone sufficient in the absence of some intelligible relation of essences between antecedent and sequent. 1 For this alternative see Kemp Smith, Philosophy of David Hume, chs xvi-xviii, App. If this was indeed Hume's view, his restraint in making it known, and his failure to draw the obvious conclusion, are perhaps natural but not the less regrettable. PROLEGOMENA 25 For causation is not merely a process of durational transition, but involves necessity which must be founded in the natures of the antecedent and sequent. It is little wonder, therefore, that empiricists and positivists who resist the introduction of principles that transcend the schemata of time and event reject the notion of natural causation, or, what is the same thing, reduce it to a function of probabilities of succession taken as statistically computed. In this connection we must note also what is generally overlooked by those who take our knowledge as beginning from observed 'facts,' 'events,' or 'data,' and proceeding to principles and theories, that the antecedent of any singular event taken strictly as singular is never a single event but an indefinitely great mass of events. Even if we seek to restrict these to those which are (in Lord Balfour's locution) 'relevant' the antecedent must remain extremely complicated and intellectually unwieldy. This complication is commonly mitigated or concealed by taking the events as singular in a special manner, viz. as 'instances' of a general kind, and thus named. When, therefore, we speak of one event as causing another we are apt to think of the kinds rather than the instances, and to suppose that one kind of event can be the cause of another kind. But kinds, being abstract universals, cannot be natural causes, and it is in their singularity that alone the instances can operate. Yet however firmly we may grasp this principle it seems impossible in this type of approach to avoid imputing to the instances causal relations abstractly conceived as if they were the relations of the kinds. But if a singular antecedent is to be properly causal its causality must likewise be singular. Its operation cannot be mere participation in the impossible operation of its kind. Nor can this paradox be avoided by conceiving the kind, not as an abstract universal but as an indefinite set of singulars, and the causal relations of the members of two kinds as no more than statistically computable probability of succession. For if the members of the sets are genuine singulars the sequence of one pair of members of two sets cannot depend on the manner in which other pairs are related. Nor, it seems, do those who favour this way of thinking suppose this - their object being to discredit the notion of causation as operation rather than to make it intelligible."


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