Why Deductive Fine-Tuning Arguments are Weak

by Max Andrews

In a correct deductive argument if the premises are true the conclusion is true regardless of whether or not further evidence is considered.  There must be a reasonable connection or relationship between the conditions in a deductive argument (in the instance of implication).  Consider the argument, as modus ponens, that if the moon’s core is made of cheese then my desk is made out of mahogany.  What relationship do these two conditions have?  The truth-value is valid (F-T-T).  However, I recognize that this is merely a preference, which is, at times, convenient.  When making a novel explanans and prediction the relationship between the conditions may not be epistemically evident.

There are generally three options, which are often considered as an explanation for the fine-tuning data: chance, necessity, a combination of chance and necessity,[1] or a fine-tuner.  One immediate problem in implementing explanatory options in a deductive manner is that the first premise may be false wherein it may be lacking in options and the argument still is valid.  When these options are used in a [strict] deductive argument[2] it may appear as:

  1. The fine-tuning of the universe is due to either physical necessity, chance, or design.
  2. It is not due to physical necessity or chance.
  3. Therefore, it is due to design.[3]

From the very onset of the argument it may be unsound.  Perhaps there are more options to be considered in premise 1.  It would still be valid but how strong of an argument, or how convincing, would it be if the options given were restricted?  An objector could merely appeal to an option not given, whatever that may be, perhaps 1 is not exhaustive or nuanced enough, and the argument rests stillborn from the very beginning.

In regards to this specific argument, if the hypothesis of mindless chance[4] processes entailed that it is impossible that cosmic environments are brought about to allow for biological evolution to occur and for organisms to exhibit delicate adaptations, then a quick application of modus tollens would sweep that hypothesis from consideration by merely positing not-mindless chance.  However, it’s not impossible that mindless chance processes should produce cosmic environments suitable for cosmic evolution and biological evolution to occur.  It’s merely improbable that such conditions should be brought about.[5]  The manner in which Craig presents this argument has a hidden premise of induction or abduction.  The problem is that it isn’t clear.  This hidden premise could be taken as induction or abduction and with no explication it weakens the case more than it already was by setting it up in a deductive manner.


[1] A combination of chance and necessity may seem contradictory, but the way it’s used as an explanans allows for a harmonious compatibility.  For example, consider the bio-chemical structure of a DNA strand, which is composed of a sugar-phosphate backbone and four different nucleotides as the rungs.  Because of the chemical structure adenine always pairs with thymine and guanine always pairs with cytosine.  Guanine and thymine bond in a DNA helix.  This would be an example of the role of necessity.  This chemical necessity combines with chance when we consider the order of the sugar-phosphates.  There’s no chemical bond, which necessitates the order in which the sugar-phosphates are positioned vertically in the helix.  A rung of adenine and thymine may be followed by a guanine and cytosine or it may simply be repeated.  There’s no chemical law requiring a specific order of the sugar-phosphate bonds.  This is simply an example from biology.  Examples can be given in physics and cosmology as well.  For instance, Stephen Hawking argues that given the law of gravity (a necessity) a universe will form (chance).  See Stephen Hawking and Leonard Mlodinow, The Grand Design (New York: Random House, 2010), 173-81.

[2] An abductive argument may appear in a deductive manner (i.e. disjunctive) but that doesn’t necessitate that it is a deductive argument.  I’m using the word ‘strict’ to indicate the difference between forming the abductive argument in a similar structure and an actual deductive argument.

[3] Design could be exchanged for fine-tuning.  William Lane Craig uses this form of the argument in Reasonable Faith ed. 3 (Wheaton, IL: Crossway, 2008), 161.

[4] It’s important to qualify this explanatory hypothesis, contra fine-tuning or design, because mindless implicitly entails non-fine-tuning or non-design.  Craig does not make this distinction in the form of the argument but throughout his explicated argument it will become apparent what he means by ‘chance.’  Chance is still compatible with fine-tuning or design.

[5] Elliott Sober, “The Design Argument,” in God and Design ed. Neil A. Manson (New York: Routledge, 2003), 33.

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