Introduction to Philosophy of Science


Hello everyone!

I wrote this two weeks ago and for some reason saved it as a draft instead of posting it, so here it is now:


To help get my own thoughts in order and to jump into this whole “philosophy” thing, I’d like to define a few definitions from my early classes.


Deduction vs. Induction

Deduction is an argument whose conclusion is guaranteed by it’s premises (assuming the premises are true).  An example: It is windy in London.  If it is windy, John is wearing a windbreaker.  Therefore John is wearing a windbreaker.

Induction, in turn, is the act of basing predictions on past observations.  For example: Every time I’ve come near fire, my skin has been burned.  Therefore all fire burns skin.

Whereas deductive reasoning uses evidence to guarantee the truth of the conclusion, induction merely offers support of the conclusion.  I have no way of knowing that every fire is hot without testing it every time, but the notion that all fire is hot is supported by my past observations.

David Hume offers a famous objection to the validity of induction.  First, he refutes the “uniformity of nature” (the idea that nature follows consistent rules that allow the future to be predicted by the past).  As an example of this non-uniformity, Hume offers the example of a chicken that has been raised by a farmer.  No matter that for every day of the chicken’s life it has received food from the farmer, one day the farmer will instead wring the chicken’s neck for his own dinner.  In this instance the chicken inductively relying on the farmer for daily food will one day lead to the chicken’s death.  Nevertheless, Hume admits that some uniformity exists in nature, allowing for often true predictions to come out of inductive reasoning.  His problem with induction comes from its justification.  He says that induction is justified because it often works – often, one can observe, the past can be effectively used to predict the future.  This is in itself a form of induction, and to base the validity of induction on inductive reasoning is a cyclical (and therefore invalid!) argument.

Karl Popper has a response to this, writing that it is wrong to discuss the validity of induction because predictions (or theories) are not in fact based on induction.  Rather, theories are put forth based on preliminary observation, but rather than being “confirmed” by subsequent observations, theories can only be falsified or corroborated – they can be shot down or survive for further trials.  Therefore it cannot be stated that “all fire is hot” is a true statement; instead, one could say that no fire has yet been found that is not hot.

Another example, called “The New Rule of Induction” offers an example of a failure in inductive reasoning:

The new riddle of induction introduces the language L’, identical to English except that blue and green are replaced with “grue” and “bleen”.

An object is “grue” if it is green before time t or blue after time t.

An object is “bleen” if it is blue before time t or green after time t.

Given a series of observations (before time t) that all emeralds found are green (or “grue” in L’), an English-speaking agent would induce that subsequent emeralds will be green.  Similarly an L’-speaking agent would induce that subsequent emeralds will be “grue”, which, after time t means that the agent expects emeralds to appear blue (as after time t “grue” is a blue object).  This leads to translational contradiction, as the two agents, using the same inductive logic, came to two different conclusions about the appearance of future emeralds.

I’m not fully convinced by the new riddle of induction.  I think that, if language L’ existed, agents would not only note the physical appearance of the emeralds in observations, but would also note the time of the observation.  As very few objects change color cyclically over time (the sky being a notable exception), L’-speaking agents would, in my opinion, not be so stupid as to expect the color of stones to change with time just because their language is time-sensitive.  Inductive reasoning would tell them that most “grue” objects which are green before time t (lily pads, grass, etc ..) become “bleen” after time t because they remain green.  Therefore if they observed a series of green emeralds before time t they would expect to see “bleen” emeralds after time t because this how green objects have in the past behaved.


Definition of Science

Another interesting concept I’ve been introduced to is Karl Popper’s definition of science.  While most people would instinctively define science as theories methodically based on observation and tested under constrained conditions, Popper offers a different definition.  He says that science is defined by “risky” predictions – the riskier, the more scientific. Scientific theories must be testable, refutable, and interesting.  A “safe” prediction (you will get sick in the next year) may be testable, but is less scientific than a more specific prediction (you will have a cough starting from November 4th and lasting 11 days).  This of course allows many seemingly non-scientific theories to call themselves science.  A medium can claim to have scientific predictions about the future of your love-life and offer incredibly specific visions, but this does not make them “good” science.  Such theories are generally either easily falsified or are so vague as to make them not very scientific to begin with.



I’ve also included some pictures I’ve taken of London and from my trip to the Cliffs of Dover last weekend.








Information taken from:

Goodman, N. ([1954] 1983) Fact, Fact, and Forecast, 4th ed., Cambridge(MA): Harvard UP, Ch. 3.

Norton, J. (2005) ‘A Little Survey on Induction’, in P. Achinstein (ed.), Scientific Evidence: Philosophical Theories and Applications, Baltimore: John Hopkins University Press, pp. 9–34.

Popper, K. (1963) ‘Science: Conjectures and Refutations’, in M. Curd et al. (eds.) Philosophy of Science: The Central Issues, second edition, New York: W.W. Norton & Company, 2012.


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