Revised 6/2/05
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An Introduction to Syntax 
and the Logic of David Hume
Portrait of 
David Hume
Allan Ramsay
(1713 - 1784)
[On Yeat's Vision] "... it suggests what seems to me on other grounds highly probable: that a good deal of our thinking is elaborated from subconscious diagrams. This comes out not only in the geometrical figures we use, 'a point of view,' 'a sphere of influence,' 'a line of action,' and so on, but also in the spatial implications of the most ordinary particles: 'beside,' 'between,' 'on the other hand,' and the like."-- Northrop Frye, Fables of Identity, p. 230.

      For the past few years, my students have had to analyze the following sentence as part of our work on clauses:

As we were still in our Renaissance costumes from a previous performance, a number of people followed us into the cathedral.
Most of the students can find the beginning and the end of the "As" clause, but when I ask them what the clause chunks to, most of them are lost -- they do not see the cause/effect relationship between the narrator's group being dressed in Renaissance costumes and their being followed into the cathedral. We are, of course, studying "grammar," but I began to wonder what happens when students meet similar sentences in "content" courses. Suppose these students were reading the text, not for grammar, but for content, and suppose that I asked them "Why did the people follow them into the cathedral?" Many of the students would get the question wrong. I know, because when they tell me that they do not know what the clause chunks to, I ask them that question next -- and many still have trouble answering it. 
     For years I have been telling students that it is the "little words" that give them the most problems, and, as I began to think about that, I realized that most of those "little words" are syntactic connectors. My students in my Introduction to Literature course, for example, also have trouble with "as." Donne's "Valediction Forbidding Mourning" also begins with "As."
As virtuous men pass mildly away, 
      And whisper to their souls, to go, 
My students almost without exception interpret this "as" as establishing a temporal relationship, and thus they interpret the entire poem as being about the speaker's death. The little words, the syntactic connectors, often cause the most problems, and I would like to suggest that the study of syntax is an excellent place to address some of those problems. To do so, we need to think about "thought."
       Although I have been unable to find the specific reference, it was, I believe, Ann Berthoff who defined a thought as "a mental apprehension of a relationship between an A and a B with reference to a C." That definition has continued to intrigue me, and it has done more so since I became familiar with the philosophy of David Hume. If I understand him correctly, Hume explains human understanding in terms of perceptions and logic. Our perceptions give us concepts on which we then operate with logic. I would like to suggest that perceptions become embodied in words, and that syntax  (grammatical structure) expresses the logical relationships (Berthoff's "thoughts") which we perceive among the concepts. 
     If this is true, then a conscious, analytical knowledge of syntax can be integrated into a fundamental study of logic.  Hume claimed that logical relationships fall into three categories -- identity, extension, and cause/effect. How does syntax convey these relationships?


    Nouns, especially proper nouns, identify, but I doubt that either Berthoff or Hume would consider a name as a thought or logical relationship.  Perhaps the most basic syntactic construction to express identity is the S / V / PN pattern.

The S / V / PN Pattern

     In a sentence such as Mary is president, we have "Mary (an "A"), and "president" (a "B") embedded in an S / V / PN pattern which itself expresses the relationship of identity. Among other things, the S/V/PN pattern is the expected beginning to any formal definition. Definitions are expected in many courses, but, because grammar is taught so poorly and inconsistently, teachers cannot explain this to students. It is simply meaningless to students who cannot identify the pattern.


     An appositive is, from one point of view, a reduction of an S / V / PN pattern: Mary is a biologist. Mary, a biologist, studies marine life. Thus, whenever we are dealing with appositives, we are dealing with a logical relationship of identity.

The S / V / PA Pattern

     Within Hume's three categories, it seems that the S / V / PA pattern would also fall under identity. The tomatoes are big describes the tomatoes and thus helps to identify them. 


     If we accept the S / V / PA pattern as expressing identity, then most, if not all, adjectives must also be seen as expressing the same relationship since transformational/generative grammar has shown that a sentence such as Tony grows big tomatoes is a combining of Tony grows tomatoes. The tomatoes are big.

Prepositional Phrases and Subordinate Clauses

     Having accepted adjectives into the group of grammatical structures which express identity, it seems that we must also make room for prepositional phrases and clauses which function as adjectives: The boy in the straw hat stole my banana. The boy who is in the straw hat stole my banana.


     By "extension," Hume seems to have in mind extension in space and time.Most people don't think of space and time as involving logical relationships, but if it was good enough for Hume, it is good enough for me. This is especially true since primary school students often need to learn to get details of space and time into their own writing. Thus the logical concepts of space and time can be an excellent way of introducing primary school students to the study of logic. 

Prepositional Phrases

     Many prepositions are used to indicate spatial and/or temporal relationships: The house is beyond the hill. After Sue, Bill sang his song. Note, however, that the same phrase which expresses extension may be used to express identity. In The house beyond the hill is not for sale, "beyond the hill" is used to identify which house is being talked about.


     Adverbial clauses of time and place probably all fall under the category of extension. In After Sue sang her song, Bill sang his, we have, in Berthoff's terms, (A) "Sue sang her song," and (B) "Bill sang his song," with a relationship (C) in time indicated by the subordinate conjunction "After."  Likewise for place, I saw him where the accident occurred establishes a spatial relationship between "him" and "where the accident occurred."

Nouns Used as Adverbs

     Nouns used as adverbs establish spatial or temporal relationships. In The accident occurred five miles from here, "five miles" establishes spatial relationship between the accident and "here." In temporal relationships, as in He worked all day, we could consider the (A) to be "He worked," and the (B) to be the noun phrase "all day." The grammatical function of the noun phrase (Noun Used as an Adverb) is the (C) the temporal relationship between his working and "all day."


     Although it would seem that basic cause/effect logical relationships would need little explanation, in working on fallacies with college Freshmen I have found that many students have real problems in identifying cause/effect statements.

Prepositional Phrases

     The most obvious preposition for expressing a cause/effect relationship is "because of" -- Sam missed class because of illness.  Phrases which express purpose also come under this category. In He did it for her, the implied cause is his desire to please her or do as she desired.


     Clauses of cause, purpose and result obviously fall into this category. One of the most interesting questions here is the use of "for" and "so" as conjunctions. (Click here for more on this.)


     Infinitives are frequently used to express purpose: She worked hard to win the game.

Noun Absolutes

     Some noun absolutes clearly express cause/effect relationships. In Mary being absent, Bill acted as president, most readers will see her absence as the cause of his acting as president.

Beyond Hume?

     I am not competent enough to be a serious critic of Hume, but in the course of studying the logic of syntax, I have found what appear to be "logical" relationships that are not clearly included in Hume's triad.

Same and Different

Logical Operators: "And," "Or," and "But" (Coordinating Conjunctions)

     In their discussions of fallacies, philosophers refer to "and" and "or" as "logical operators." (See Downes.) I have added "but" because it appears to have a similar function. "And" reflects a sameness, but not identity. The sameness appears not in the concepts themselves, but rather in their contexts. Within clauses, this can be seen in the fact that the clauses can almost, if not always, be restated as two separate clauses with the context repeated:

She plays baseball and football.
She plays baseball, and she plays football.
The use of "and" to join main clauses probably has a similar function. To my knowledge this has never been studied, but it would be interesting to see which main clauses writers join with "and" and which they do not.
     The fame of "or" as a logical operator is most obvious in Boolean logic. "Or" seems to require that either the concept or the context be identical (or at least similar), the other being different: For example, if the concept ("boat") is identical, the context is different -- The boat will float, or sink. If the concepts ("boys" and "girls") are different, the context is identical -- Either the boys or girls will win.
     When used as a coordinating conjunction, "but," like "or," implies both similarities and differences -- He wanted to play, but he couldn't (play). It would be interesting to see if "but" always implies some sort of negation or exception, but I am unaware of any studies that explore this question. [Note the implied negation -- There are no such studies.] Such a study, of course, would require the collection of numerous examples, preferably from recognized "good" writers and from novices, and then the exploration of the relationships expressed by "but."


     Many writers have, and still do, use a semicolon to join main clauses which include implied similarities and differences. My favorite example of this is still He went swimming; she did the dishes. In order to understand the implied difference in this example, however, one must also use another logical operation, movement from the specific to the general -- He played; she worked. The semicolon, in this function, appears to be close to the ", but."

General / Specific

Colons, and Dashes

     Whereas semicolons can be used to emphasize contrasts in the ideas in main clauses, colons (in formal writing) and dashes (in informal writing) are often used to express a general / specific relationship: The weather is bad: it's twenty degrees with a slow drizzle. 


     Dashes are also used to set off appositives that reflect a general / specific relationship They saw the animals at the zoo -- the lions, tigers, bears, monkey, and giraffes.

Comparison / Contrast

     Comparison / Contrast is, of course, related to similarities and differences, but a focus on comparison / contrast involves specific syntactic markers, namely the prepositions "like" and "as" and the comparative and superlative forms of adjectives and adverbs. It also involves (sometimes implicitly) the notorious "than," which students have a bad habit of confusing with "then."

Manner (or Method) -- Responses to the Question "How?"

     I'm not sure that logicians would consider "manner" a logical relationship, but a quick scan of students' revisions of the Aluminum passage suggests that manner (method) needs to be considered as a separate category. Whereas some students treated Workmen extract these other substances from the bauxite. They grind the bauxite. as two statements of fact, others emphasized method -- Workmen extract the other substances by grinding the bauxite, .... This version has the effect of distinguishing "extract" as the purpose, and "grinding" as the method for achieving that purpose. Some students did the same with Workmen separate the aluminum from the oxygen. They use electricity -- Workmen separate the aluminum from the oxygen by using electricity.


     Adverbs are, of course, often used to express manner - She stood rigidly at attention.

Prepositional Phrases

     As suggested above, the most common preposition for expressing manner is "by."


     In his discussion of clauses of manner, Roberts claims that the most commonly used conjunctions are as, as if, as though, and in that. (Understanding Grammar, 321).


     In their revisions of the Aluminum passage, some students used gerundives -- Using electricity, workmen separate the aluminum from the oxygen.


     This essay is far too short to reach any conclusion, but it does suggest another way of looking at syntax. Syntax is usually considered to be only "the relationships among the words in sentences." I hope that this essay has demonstrated that many, if not all, of those "relationships" are logical, and that instruction in syntax can, and probably should, be extended into basic instruction in logic.