This Critical Notice was published in Dialogue, (1995) vol. 34, no. 4, pp. 797-806.
Topology in Informal Logic: Slippery Slopes and Black Holes
Douglas Walton, Slippery Slope Arguments
(Oxford: Oxford University Press, 1992), xiii+296, and
James Davies, Ways of Thinking
(New York: Peter Lang, 1991), xiv+258.
NORMAN SWARTZ Simon Fraser University
The commonalities of Douglas Walton's Slippery Slope Arguments and
James Davies's Ways of Thinking are obvious: both are written by
Canadian philosophers; both lie within the broad field of informal
logic; and both make appeals in support of dialogical reasoning. But
there the similarities end. The former is the work of a prolific author
writing a treatise focusing narrowly on one topic within informal logic;
the latter is the product of a newcomer to book-writing, and his is a
textbook intended for beginning students.
Judging from my own experience and from conversations
with colleagues, it seems that philosophers, generally, tend to be slow,
methodical, readers. But if ever a book warranted speed-reading, it is
Walton's Slippery Slope Arguments. Walton is, to be sure, a
high-minded philosopher; he writes serious philosophy; there is good
philosophy within the covers of Slippery Slope Arguments. Even so, the
book is heavily padded, and – like some of his previous work –
maddeningly repetitious. Here is one of numerous examples (this one,
you will notice, occurring within the span of just two pages):
Practical reasoning is a goal-directed type of
argumentation which takes knowledge of an agent's situation into account
in guiding the agent on how it is reasonable to act in a situation of
incomplete knowledge (pp. 87-88).
The conclusion of a practical inference is an imperative to a course of
action for a particular agent (p. 88, top of page).
Practical reasoning is a goal-driven, knowledge-based, action-guiding
kind of argumentation that concludes in a practical imperative of action
in relation to the (usually imperfect) knowledge that an agent has of
ways and means to proceed in a particular situation (p. 88, middle of
The conclusion of an instance of practical reasoning is an imperative
that directs a planner (or agent) to a specific course of action (or
inaction) in a particular situation, as it is known to the planner (p.
There are also occasional lapses into banality:
The planner tries to forecast or imagine the possible
good consequences of the planned action, and also the possible
bad consequences. The good or favorable consequences tend to support the
action being considered, while the bad or negative consequences have the
opposite effect (p. 90).
This book cries
out for the scissors of a ruthless editor who would have left much of
the text on the cutting room floor.[Note 1]
In an earlier review[Note 2], I characterized
another of Walton's books[Note 3] as containing
enough good material for a book half its size. In the present instance,
Walton calls this volume a monograph To this I would reply that
it contains enough good material for a stout pamphlet.
Another failing common in Walton's writings
is his predilection to
use standard philosophical terminology in sloppy ways, especially when
writing of causation. Example: "causality is not a matter of necessity,
especially when a long sequence of causation is concerned" (p. 102). One
must be puzzled over the appending of the qualifying clause. How could
necessity depend on the number of steps in a causal sequence?
Yet, in spite of the dross and the
frequent clumsiness, there is – as I have said – a core of good
philosophy in this book. The chief merit is that – probably for the
first time – a writer pulls together material from many writers
(esp. Govier; Little, Groarke, and Tindale; and Perelman
and Olbrechts-Tyteca) and synthesizes from it a sustained
examination of slippery slope arguments.
Walton begins his study by emphasizing
that slippery slope arguments
are not invariably, or even for that matter usually, fallacious
arguments.[Note 4] For example, I recall my own father
warning me of the dangers of beginning smoking, how the habit may become
addictive and be extremely difficult to break. His was a slippery
slope argument: "If you begin to smoke, you may become a heavy
smoker and find it very difficult to quit." There was nothing
fallacious about his argument; it was a perfectly sound piece of
The problem then becomes that of attempting
to classify the kinds of
slippery slope arguments; of trying to distinguish sound, or proper,
uses of slippery slope arguments from fallacious ones; and, finally, to
review strategies for refuting or rebutting fallacious uses of such
In the classificatory scheme Walton devises,
there are four kinds of
slippery slope arguments: (1) the Sorites; (2) the Causal; (3) the
Precedent; and (4) the so-called Full. Oddly, Walton never raises the
question whether this scheme is exhaustive.
The Sorites version of the Slippery
Slope argument involves
the gradual extending of a vague term from cases where it
clearly applies to cases where it does not apply or does so
only problematically. A typical example is to be found in
disputes raging over the morality of abortion. If it is conceded that
it is immoral to kill a fetus just prior to birth, how can one draw a
line after which it is immoral to kill a fetus but prior to which it is
morally permissible? As we all know, some persons have used slippery
slope arguments, in particular the Sorites version, to insist that no
such line exists: that abortion, from the very moment of conception, is
The Causal version is illustrated in
the 'Domino-theory' put forward
to justify American involvement in the War in Vietnam: "If Vietnam is
allowed to fall to the Communists, other countries in Southeast Asia
will similarly fall."
The Precedent version (typically)
involves arguing against a certain
proposal because there are similar cases which would seemingly merit
similar treatment and thus would expand, undesirably, the scope of the
initial proposal. For example: "Allowing French parents to choose to
send their children to French language schools which would have public
support would be a precedent for allowing parents of Indian, Ukrainian,
German and many other language groups to do the same thing. …" (p.
The descriptive title "full" that Walton adopts (borrowing
from Govier) for his fourth category is somewhat misleading (p. 162).
For it carries with it the implicit suggestion that the other three
kinds of slippery slope arguments are not 'full', i.e. are somehow
sketchy or incomplete. Perhaps a more apt term might have been something
of the sort "multidimensioned" or "composite". In this fourth, last,
kind of slippery slope argumentation, no fewer than eight features are
present: "(1) argument from gradualism, (2) argument from consequences,
(3) practical reasoning, (4) argument from analogy, (5) argument from
popular opinion, (6) argument from precedent, (7) causal argumentation,
and (8) the sorites type of argumentation" (p. 161). (Needless to say,
such complex arguments will tend to be rather lengthy, not
lending themselves to quotation in a review.) Walton offers examples
of 'full' slippery slope arguments in case studies involving euthanasia,
censorship, and medical research using fetal tissue.
Throughout his discussions, Walton is
concerned with laying out the
logic of slippery slope arguments and with the kinds of moves one might
make in practical argument to support or rebut a slippery slope
argument. He is much less concerned to examine the particular strengths
and weaknesses of specific examples. Thus readers hoping or expecting to
find in this book detailed and lengthy examinations of the substantive
issues involved in major contemporary disputes in which slippery slope
arguments feature prominently will be
disappointed.[Note 5] For example, after
having invoked the abortion issue several times in the book
for illustrative purposes, Walton's final word leaves the matter hanging
in an extraordinarily indecisive fashion:
Both [disputants] had equally strong arguments, and as a
result, neither argument gained an ascendancy that could resolve
the dispute. A good tactic to break the deadlock would be for one side
or the other to take the initiative and make a case for the beginning of
personhood at some point on the continuum other than the two poles of
conception and birth, rejected by the other side.
For example, if one of them were to
argue that a fetus becomes a
person at the last point in the first trimester, it would break the
deadlock. But of course this argument would have to be backed up by good
reasons for picking this point, or else the other party might insist
that this point is arbitrary, using the slippery slope argument again.
In short, this book examines the dialogical
structures of four kinds of slippery slope arguments; it does not, but
neither does it pretend to, examine the contents of specific disputes
that turn on slippery slope arguments.
Where Walton's book, to date anyway,
has the field pretty much to
itself (a computer-search of several major university libraries turned
up no other book devoted entirely to the logic of slippery slope
arguments), Davies's Ways of Thinking must compete in a market
supersaturated with books, many in late editions and by well-known
authors (and in some cases, teams of authors) backed by the resources of
several of the largest textbook publishers. To carve out any piece of
this cutthroat market, Davies's book would have to offer something both
unique and worthy.
There is no question that Davies's book
is unique. Indeed it attempts to create a wholly new sub-genre
within informal logic. Davies explains:
This is a "thinking book" with a
difference – besides developing a method of critical thinking in general
conformity with college and university practice, it sets such a method
within the larger context of different ways of thinking. Such "ways of
thinking" are, surprisingly, alien to contemporary academic practice
with its dependency on one way of thinking, that which has
become enthroned in science and technology, namely linear thinking.
This dependency has been largely unreflective … (p. xi).
The frame of reference of this book is phenomenological and existential.
'Existential' means that philosophy is related to history and existence
and it is not adequate thinking and perception without reference to
these realms. … 'Phenomenology' means openness to the phenomena as
they are, approaching them without preconceptions; no theories or
'descriptions' are accepted which prescribe antecedently how phenomena
are to be perceived. (p. 246).
In addition to 'linear'
thinking, Davies distinguishes five others: lateral, literary,
meditative, historical-existential, and metaphysical.
If Davies were able to make good on
his stated program, Ways
of Thinking would be one of the most important philosophical books of
the decade. For the thesis he is advancing is audacious, and, if
sustained by evidence and argument, would be nothing short
of revolutionary. Unfortunately, the support for his thesis is so weak,
unconvincing, and clumsy that it actually undermines his program.
Having expressed his displeasure at the
accorded what he calls 'linear' thinking, Davies begins by devoting six
(out of ten) chapters precisely to advancing this mode of thinking (some
58% of the total pages).
The book is a shambles: it is naive (in
the worst sense of
that term) and is error-ridden. No chapter escapes presenting some major
falsehood. "A conclusion, in philosophical argument [which Davies
illustrates with a trivial syllogism], is that proposition which follows
from the reasons and breaks new ground"
(p. 8). Davies appears to
have forgotten, or overlooked, Mill's and others' worries whether every
deductively valid inference is a petitio principii. "An argument
contains two or more propositions, one of which follows logically from
the other(s) as a conclusion" (p. 9). Indeed?! On such an account, there
would be no deductively invalid arguments, no inductively valid ones,
and no inductively invalid ones.
In his explication of Venn diagrams (p. 23), Davies writes as if the
invalidity of the inference from "All S is P" to "All P is S" validates
the inference "All S is P ├ ∼(All P is S)" (p. 23).
In his explanation of necessary and sufficient
Davies includes some mighty queer examples: "Election, in a democracy,
[is] a necessary condition of sovereignty" (p. 43). Did I overlook the
Queen's being elected? "Education is a necessary condition of
professional certification" (p. 43). Legally necessary, perhaps, but
surely not causally necessary. "Ice is a sufficient rather
than necessary condition of hockey because hockey can be played on grass
and floor as well as ice" (p. 43). Here Davies seems to be presupposing
that if a condition is not a necessary condition, then it is sufficient!
But not only is that general presupposition false, his specific
conclusion is likewise, since clearly there are instances of ice, e.g.
the surface of my driveway two winters ago, where no hockey whatever has
been played. "A quarter is a sufficient, but not necessary condition, of
there being a penny in my pocket" (p. 45). That's strange: here in
Canada, quarters are made of nickel, while pennies are made of copper.
The symbolism of the sentential calculus
— viz. "∼", "•", "∨", "⊃", and
"≡" — is cursorily introduced (p. 39), seemingly more as a
gesture than with conviction. The symbols are not given truth-table
definitions; no inference rules are offered for their use; and they are
actually used subsequently on only four pages (40-41 and 43-44).
On page 75, Davies explicates the denial of the
universal affirmative, "All politicians are dishonest", with the
ambiguous barbarism, "All politicians are not dishonest".
Davies argues that deductively valid arguments are
both truth-preserving and falsity-preserving: "If
premise-propositions are false or problematic, the conclusion of the
argument will also be false or problematic unless the reasoning is
faulty (that is, fallacious, in which case it might fallaciously be
true)" (p. 170). Nonsense. Any reader who has had even a modicum of
exposure to a good logic course will find it a trivial matter to
generate counterexamples, e.g., "Former Prime Minister Trudeau has
six sons. Therefore Trudeau has at least two sons." The premise(-set) is
false; the conclusion is true; and the reasoning is not fallacious.
In chapter seven, Davies offers explications of four
different theories of truth, to which he gives the names,
"correspondence", "coherence", "pragmatic", and "ontological". Although
in the first three cases he claims to be explicating
traditional theories, the analyses given can be considered, if not
simply bizarre, then, at the very least, glaringly inept. For
example, in what Davies calls the "correspondence" theory, we
find something remotely akin to a Tarskian theory, but only remotely.
Davies's version seems to be a cocktail of semantic features along with
epistemological ones (in particular, verificationist ones). "If one says
'E=mc2', for the formula to be true, there should be a
correspondence between it and a physical experiment, or series of
experiments, in which it is demonstrated" (p. 184). To this he adds,
"there are a number of different kinds of correspondence in surprisingly
diverse areas. We cite three: scientific, superstitious, and religious"
In his discussion of coherence, Davies
attributes to Gödel (whose
given name Davies consistently misspells as "Curt"), a perfectly
preposterous proof, viz. "that all mathematical-logical systems will
eventually generate paradox" (p. 185). He then continues: "The
consequence of the truth of this theorem is that coherence must be
broadened sufficiently to include it [i.e. paradox]. It is to be noted,
also, that paradox differs from inconsistency because it is a special
situation in which a proposition is both true and false. The fact that a
system may generate paradox does not, however, mean that inconsistency
is accepted into a system as a general rule. Paradox is an exception to
the rule. It appears to be the case that, in a complete system, even
paradox coheres" (pp. 185-6). I am sure that this quotation does not
itself cohere [sic].
Jumping ahead to the 'ontological' theory of
truth, we read: "The
ontological theory provides a theory by which literary expression can be
related to truth. Heidegger believes that truth is 'the unveiling of
being'. Using this belief, it is possible to understand literary
thinking as making possible such an unveiling through analogy, metaphor,
myth and symbol" (p. 187). I wonder, will beginning students in critical
thinking – the intended audience – be able to make sense of this? I
Chapter eight is devoted to dialogical thinking, a topic which has
occupied other writers, e.g. Walton, much in recent years and whose
writings are far more penetrating and illuminating.
Chapters nine and ten are, finally, given over to arguing
that attention should be paid to 'other modes' of reasoning:
the aforementioned lateral, literary, meditative, and metaphysical. If
there were any merit to be found in this book, it would have to be in
these last two chapters.
Not surprisingly these latter chapters are of no better quality than
their predecessors. Chapter nine suffers from a complete ignoring of the
difference between the context of discovery and the context of
justification. Few, if any, other authors nowadays present the fare of
standard informal logic textbooks as canons of discovery, and to extol
the (supposed) creative virtues of 'lateral' thinking, etc. in contrast
to what Davies calls 'linear' thinking, is to egregiously misrepresent
the claims made on behalf of the latter.
No one who has read Popper on falsifiability could ever seriously
advance the inane argument Davies does on page 223. There, Davies is
trying to commend the technique of 'free association'. In a reportedly
actual case (no reference given), someone 'free associates' on the word
"air". The first few words, we are told, have 'obvious' connections to
"air", but then succeeding words – viz. "artery", "fair", and "art" –
seem not to. But Davies has no trouble finding the (supposed)
connection: "There is, initially, no apparent connection but, on
reflection, it is noted that arteries carry oxygen, a vital component of
air" (p. 223). Davies needs to read Popper's critique of Adler: "What, I
asked myself, did it confirm? No more than that a case could
be interpreted in the light of the theory. But this meant very little, I
reflected, since every conceivable case could be interpreted in the
light of Adler's theory…"[Note 6] Like
Adler, Davies ingenuously believes that the impossibility of
disconfirmation is powerful support for a theory. He then continues:
"Everything is related rationally to everything else, so that, however
disparate any two things may appear to be, they turn out to be
related. … The idea here is that a (rational) relationship can be
discovered between any two entities whatsoever. … If everything is
somehow related to everything else, lateral thinking is not
necessarily unrelated, in some way, to what you are reasoning about no
matter how remote or unconnected it may appear to be. If this is
so, lateral thinking is an essential and powerful catalyst to thinking"
(pp. 224-5). I will not even attempt to catalog the cascade of blunders
in this passage.
The ensuing few pages contain advice to "relax in the consciousness
of infinity"; repeat a mantra; and "utter quietly the word 'OM', an
'unstruck sound' or 'primordial vibration'" (p. 230). In the final
section, "Metaphysical Thinking", Davies thoroughly obscures the
act/content distinction, arguing that thinking about metaphysical
issues is a different manner of thinking than exhibited in, e.g.,
thinking about scientific matters.
In short, what one finds in this penultimate chapter is the sort of
blather contained in scores of books which line the shelves of
third-class bookstores in shopping malls. We have here, certainly not
all, but many of the buzzwords of new-age 'metaphysics' and its 1960's
The final chapter, "Thinking and Existence", while containing some
viable claims about collective reasoning, remains, for the most part,
vapid and distressingly obscurantist. "For thinking to be vital at all,
it must issue from consciousness and being which are sufficiently
centered and powerful enough to be able to generate authentic
individuality" (p. 251). Davies asserts that "a centered and strong
consciousness and being can be created only through a community in which
they are celebrated and nurtured" (p. 252). He thinks that certain
communities are better suited to this task than others. His favored
nominees – but with strict reservations – include communities of
philosophers, trade unions, and theatre companies (p. 252).
I am in no position to gauge the worth of this book relative
to all other textbooks in informal logic. But this much I can say with
assurance: of the fifty or more such books currently on my shelves,
every one of them is significantly better than Ways of Thinking. Its
being reviewed along with Slippery Slope Arguments, does nothing, I
hope, to tarnish Walton's book. Walton's book, as explained, has its
flaws (mostly stylistic), but it also has very considerable merit and
warrants a place in research bibliographies in modern informal logic.
Davies's book, in contrast, deserves to be ignored.
- It would also have profited
from a copy-editor who was sensitive to misplaced modifiers. For
||This technique developed into the
technique used by Socrates in the early dialogues called the elenchus
||… in an everyday discussion of a controversial topic like
drug abuse by nonexperts… (p. 78).[ Resume ]
- Norman Swartz, "A Guide for the Disputatious",
Dialogue, 30 (1991), pp. 123-8.[ Resume ]
- Douglas Walton, Informal Logic: A Handbook for Critical
Argumentation (Cambridge: Cambridge Univ. Press, 1989).[ Resume ]
- He points out that some informal logic texts treat
the slippery slope argument exclusively as a fallacy. But then, true to
his style, he repeats the point time and again, e.g., on pages 2, 13,
15, 29, 103, 207, 242, 280, etc.[ Resume ]
- For the
latter, 'issues-focused', approach to slippery slope arguments, see
David Lamb's Down the Slippery Slope: Arguing in Applied
Ethics (London: Croom Helm, 1988). Walton's and Lamb's books
are remarkable complements of one another.[ Resume ]
- Karl Popper, Conjectures and
Refutations (New York: Basic Books, 1962), p. 35, italics
added.[ Resume ]
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