All views are only probable, and a doctrine of probability which is not bound to a truth dissolves into thin air. In order to describe the probable, you must have a firm hold on the true. Therefore, before there can be any truth whatsoever, there must be absolute truth.

Sartre, Jean-Paul

The Philosophy of Existentialism (p. 51)

I think that we shall have to get accustomed to the idea that we must not look upon science as a 'body of knowledge' but rather as a system of hypotheses; that is to say, as a system of guesses or anticipations which in principle cannot be justified, but with which we work as long as they stand up to tests, and of which we are never justified in saying that we know that they are 'true' or 'more or less certain' or even 'probable'.

Popper, Karl R.

The Logic of Scientific Discovery (p. 317)

Predicted facts ... can only be probable.

Poincare, Henri

The Foundations of Science
Science and Hypothesis (p. 155)

But is it probable that probability gives assurance?

Pascal, Blaise

The Thoughts of Blaise Pascal
Appendix: Polemical Fragments, 908

The laws of chance tell us what is probable, but not what is certain to happen. They do not predict. They do not tell us what will, but what may, happen.

de Leeuw, A.L.

Rambling through Science
Gambling (p. 88)

In short, these fundamental elements of scientific knowledge assimilate and grow, coalesce and separate and recombine, shrink and wane, die and come to life again; and while they persist they are never more than probable.

Barry, Frederick

The Scientific Habit of Thought (p. 139)

If the universe is a mingling of probability clouds spread through a cosmic eternity of space-time, how is there as much order, persistence, and coherent transformation as there is?

Whyte, Lancelot Law

Essay on Atomism: from Democritus to 1960
Chapter 2 (p. 27)

One can locate an octopus by giving the coordinates of his beak, but it would be unwise to forget that neighboring coordinates for two or three yards out in all directions have a considerable probability of being occupied by octopus at a given instant.

Walker, Marshall

The Nature of Scientific Thought (p. 65)

The theory of probability can never lead to a definite statement concerning a single event.

von Mises, Richard

Probability, Statistics and Truth
First Lecture (p. 33)

He who has heard the thing told by twelve thousand eye-witnesses, has only twelve thousand probabilities, equal to one strong probability, which is not equal to certainty.

Voltaire

The Portable Voltaire
Philosophical Dictionary
Truth

A pinch of probability is worth a pound of perhaps.

Thurber, James

Lanterns and Lances
Such a Phrase as Drifts Through Dreams

It is better to be satisfied with probabilities than to demand impossibilities and starve.

Schiller, Friedrich

Quoted in Rudolf Flesch's
The New Book of Unusual Quotations

When we want something, we always have to reckon with probabilities.

Sartre, Jean-Paul

The Philosophy of Existentialism (p. 46)

Good and bad come mingled always. The long-time winner is the man who is not unreasonably discouraged by persistent streaks of ill fortune not at other times made reckless with the thought that he is fortune's darling. He keeps a cool head and trusts in the mathematics of probability, or as often said, the law of averages.

Redfield, Roy A.

Factors of Grozoth in a Law Practice (p. 168)

"I can't pretend to understand probability math. But if the universe is so ordered, so-immutable-that the future can be told by a handful of numbers, then why need we go on living?"

Pratchett, T.

The Dark Side of the Sun (p. 22)

The very name calculus of probabilities is a paradox. Probability opposed to certainty is what we do not know, and how can we calculate what we do not know?

Poincare, Henri

The Foundations of Science
Science and Hypothesis (p. 155)

I know too well that these arguments from probabilities are impostors, and unless great caution is observed in the use of them, they are apt to be deceptive.

Plato
Phaedo
92

Take away probability, and you can no longer please the world; give probability, and you can no longer displease it.

Pascal, Blaise

The Thoughts of Blaise Pascal
Appendix: Polemical Fragments
918

The probability is, I suppose that the Monarchy has become a kind of ersatz religion. Chesterton once remarked that when people ceased to believe in God they do not believe in nothing, but in anything.

Muggeridge, Malcolm

New Statesman 1955

Uncertainty is introduced, however, by the impossibility of making generalizations, most'of the time, which happens to all members of a class. Even scientific truth is a matter of probability and the degree of probability stops somewhere short of certainty.

Minnick, Wayne C.

The Art of Persuasion (p. 167)

Messenger said, "Can you work out any equations of probability of one hitting here?"
"No sir. A hurricane has no memory. Like a coin. If a coin comes up heads fifty times, the odds on the next flip are still fifty-fifty, head or tail. But if you flip it ten thousand times, you'll get five thousand heads, plus or minus."

MacDonald, John D.

Condominium: A Novel
Chapter 26 (p. 235)

Probability is likeness to be true...

Locke, John

An Essay Concerning Human Understanding
Book IV, XV, 4

A ”poor evaluation” of the probability of anything may reflect ignorance of relevant data which “ought” to be known...

Lewis, Clarence Irving

Mind and the World-Order
Chapter X (p. 331)

Probability has reference partly to our ignorance, partly to our knowledge.

Laplace, Pierre-Simon

Essai Philosophique sur les Probabilites (p. 9)

The most important questions of life are, for the most part, really only problems of probability.
...in the small number of things we are able to know with any certainty
...the principle means of arriving at the truth ...are based on probabilities...

Laplace, Pierre-Simon

A Philosophical Essay on Probabilities (p. 1)

It is difficult to find an intelligible account of the meaning of 'probability', or of how we are ever to determine the probability of any particular proposition; and yet treatises on the subject profess to arrive at complicated results of the greatest precision and the most profound practical importance.

Keynes, John Maynard

A Treatise on Probability
Chapter IV (p. 251)

All knowledge resolves itself into probability.

Hume, David

A Treatise of Human Nature
Book I, Part IV, Section 1

A reasonable probability is the only certainty.

Howe, E.W.

Sinner Sermons (p. 23)

Whereas wisdom favors the probabilities, folly favors only the possibilities.

Gracian, Balthasar

Quoted in Thomas G. Corvan’s
The Best of Grucian (p. 38)

But if probability measures the importance of our state of ignorance it must change its value whenever we add new knowledge. And so it does.

Fry, Thornton C.

Probability and Its Engineering Uses (p. 145)

Philosophy goes no further than probabilities, and in every assertion keeps a doubt in reserve.

Froude, James Anthony

Short Studies on Great Subjects
Calvinism (p. 51)

In its efforts to learn as much as possible about nature, modem physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities.

Feynman, Richard P.

The Feynman Lectures on Physics (p. 6-11)

Secrets are rarely betrayed or discovered according to any program our fear has sketched out. Fear is almost always haunted by terrible dramatic scenes, which recur in spite of the best-argued probabilities against them...

Eliot, George

The Mill on the Floss
Book V, V

...ignorance gives one a large range of probabilities.

Eliot, George

Daniel Deronda II
xiii (p. 100)

There can be no unique probability attached to any event or behaviour: we can only speak of ”probability in the light of certain given information”, and the probability alters according to the extent of the information.

Eddington, Sir Arthur Stanley

The Nature of the Physical World (p. 315)

Deifield’s Principle. The probability of a young man meeting a desirable receptive young female increases by pyrimidical progression when he is already in the company of (1) a date, (2) his wife, (3) a better looking and richer male friend.

Deifield, Ronald H.

Quoted in Paul Dickson’s
The Official Rules (p. B-12)

We defined the art of conjecture, or stochastic art, as the art of evaluating as exactly as possible the probabilities of things, so that in our judgments and actions we can always base ourselves on what has been found to be the best, the most appropriate, the most certain, the best advised; this is the only object of the wisdom of the philosopher and the prudence of the statesman.

de Jouvenel, Bertrand

The Art of Conjecture
(p. 21, note 19)

Considine’s Law. Whenever one word or letter can change the entire meaning of a sentence, the probability of an error being made will be in direct proportion to the embarrassment it will cause.

Considine, Bob

Quoted in Paul Dickson’s
The Official Rules (p. C-32)

Fate laughs at probabilities.

Bulwer, Lytton, E.G.

Eugene Aram
Book I
Chapter 10 (p. 71)

Probability is expectation founded upon partial knowledge. A perfect acquaintance with all the circumstances affecting the occurrence of an event would change expectation into certainty, and leave neither room nor demand for a theory of probabilities.

Boole, George

Collected Logical Works
Volume II
An Investigation of the Law of Thought
Chapter XM (p. 258)

The more ridiculous a belief system, the higher the probability of its success.

Bartz, Wayne R.

Human Behavior
Keys to Success

Are no probabilities to be accepted, merely because they are not certainties?

Austen, Jane

Sense and Sensibility
Volume I, Chapter 15

He was a strange boy to be sure. There was always some ground of probability and likelihood mingled with his absurd behaviour. That was the best of it.

Dickens, Charles

The Work of Charles Dickens
Martin Chuzzlewit
Chapter XI (p. 166)

Mopworth always took a seat at a window already cracked and taped, or patched with cardboard, banking on the Law of Probability to reduce the likelihood of another rock coming in that one again before it came in another.

de Vries, Peter
Ruben, Ruben

Mopworth
Chapter Thirty-Four (p. 411)

I collect quotes whenever I can, inside CintaNotes. It's a thing I love to do. I love words and love reading books. Sometimes I will finish a book just in case there is a good quote somewhere in the end. I hope you will not mind me sharing a few quotes related to "probable" and "probability" that I've collected over time.

Hi all,

I don't want this to sound like too much of a rant. I cam to the conclusion that either a) I am pretty clueless, or b) the meaning of words (such as "probability") mean different things to me than to people with more of a trading background. This post is similar to @shodson 's thread here:

"It's a high probability trade" I just want to rant: I'm tired of reading in books/magazines/websites talk about "high probability setups" or "high probability trades" without ever publishing what the probabilities are. If you don't have numbers to support …

There are these terms like "high probability trades", and people saying that "I never take a trade unless it has at least a 2:1 return". Statements like this do not make sense to me.

Let's take high probability trades as an example. First, there is the sloppy language that really means "high probability of making a positive return", and not what the simplest interpretation of the words imply: "a high probability of occuring." By saying a certain trade is likely to be a winner, there are two probabilites involved: a) the probability that the setup/entrance is good, and b) the probability that market moves in the direction congruent with the setup at time of exit. Now, a) is fairly easily known. But, on a case-by-case basis, b) cannot be known until after the trade has occured.

Now to the second example. People saying that they only trade trades that have a X or better statistic. By saying this, they are saying that the probabilites of both the entrance and exit "add up" (multiplied, really) to their threshold statistic for entering the trade. But, how do they know their exit statistics before the fact? They cannot.

The only way to know the probabilities of any trade is to compute the statistics after the fact, from a group of trades (preferably, at least 30). From this collection of trades, we can compute statistics to wahzoo to our heart's content. But! We can only say, for example, "This group of trades has a profit factor of N." We cannot say "Because the group of trades had this profit factor, this particular trade had the same profit factor." We can go back and calculate the profit factor for a trade after that trade has occured. But, estimating the profit factor before the trade has occured (or finished) requires extrapolation of the market forward in time - something wrought with much uncertainty.

My question: Do most traders use nebulous/sloppy (maybe wrong?) terms, or am I missing something huge? Is there some way to estimate exit efficiency before the exit has occured? Am I dumb, or am I overthinking this?