Global scepticism can be resisted. Discuss
Philosophical scepticism is a less a theory and more a challenge which can be used questions any claim to knowledge.
To be more precise it asks if we have an adequate justification for anything we believe to be true. Philosophical
scepticism is sometimes described as hyperbolic scepticism as – unlike normal incredulity which simply arises from
‘everyday’ reasons for doubt (e.g., we doubt A’s claim he knows B is abroad, because we saw someone who looks just
like B moments ago) – it is willing to entertain any reason for doubt, no matter how fantastical or strange (e.g., the
brain in a vat hypothesis). While local scepticism applies philosophical scepticism to a limited range of knowledge
claims (e.g., about God or a mind-independent world), global scepticism applies it to all knowledge claims. In this
essay we will explore Descartes’s attempt – as described in his Mediations – to respond to global scepticism. We will
conclude that global scepticism can be resisted, but not in the ambitious way Descartes hoped.
After he announces that he is unwilling to accept any knowledge claim that isn’t free from doubt, Descartes begins
the Meditations by raising the Three Waves of Doubt (a series of sceptical arguments) which lead to global
scepticism. Of the three (illusion, dreaming, and the evil demon), Descartes admits that the evil demon hypothesis is
the most damaging as it seems to call both perception and thinking into doubt. However, despite this concern,
Descartes believes that even if the evil demon hypothesis is true, he knows for certain that he exists. This must be
true, because even if the evil demon is deceiving Descartes there must be an ‘I’ that is being deceived; the very fact
of doubting (a mode of thinking) is proof that he exists. I think, therefore I am. From this, Descartes goes on to
conclude that free from doubt and according to the ‘natural light’ of reason he must exist as a persistent thinking
thing.
This sounds like a promising rebuff to the sceptic but there is much in Descartes’ claim that is not free from doubt.
Firstly, as argued by Nietzsche, Descartes’ claim that he exists as a persistent thinking thing (i.e., as something that
exists over time) rests upon memory. However, without expelling the evil demon hypothesis Descartes has no reason
to trust his memory. Thus, even though we may be willing to concede that Descartes exists as a thinking thing, we
cannot say he persists over time, but only at the point in which he thinks.
However, it gets worse, because drawing on Hume, Descartes’ claim that he exists as a thing (i.e., as a mental
substance, a mind) also seems open to doubt. This is because this claim rests upon the assumption that thoughts
require a thinker, and it is not at all clear a priori or a posteriori how this is known. Firstly, if the proposition ‘thoughts
require a thinker’ was known a priori then it should be impossible to deny without falling into logical contradiction.
However, from a careful analysis of the meaning of the words in the proposition this isn’t the case (true, by
definition, a thinker requires thoughts, but thoughts don’t require a thinker). Therefore, it is not an a priori necessary
truth that thoughts require a thinker.
When we turn to the a posteriori, we can accept that Descartes has experienced thought but at no point is it clear
that he has experienced a mind, a mental substance that possess or causes these thoughts. As Hume convincingly
argues, Descartes has confused similarity between thoughts for a unified substance that possesses them (in the same
way that one might confuse similarity in the look and behaviour of individual birds moving in concert as a flock, as
the product of one unified substance). Descartes has only experienced a bundle of thoughts, not a mind or mental
substance that possesses them. This observation is further supported by introspection, which reveals an awareness
of thoughts, feelings, desires, etc., but at no point a ‘mind’, a ‘thinking thing’ that possess or causes them. Therefore,
Descartes does not have an adequate justification – neither a priori nor a posteriori – to claim knowledge of a thinker
simply based on thought.
Drawing all the previous material together, when we combine Hume and Nietzsche’s sceptical arguments, it would
seem that Descartes can only claim to know [at the point at which it is perceived] that a thought exists. This may be
enough to resist global scepticism, but before we consider this point any further, we shall turn to Descartes’s
arguments for God and physical objects.
Due to time constraints this essay will only consider Descartes’ trademark argument for the existence of God.
However, there is good reason to believe that both his cosmological and ontological argument rely on the ideas and
conclusions established by the trademark argument, and therefore if it is not sound then none of his arguments for
God’s existence are. Simply put, with his trademark argument, Descartes argues that GOD (the concept of God)
proves God exists, as God is the only being that could generate such a concept. At this point, we may protest and
Philosophical scepticism is a less a theory and more a challenge which can be used questions any claim to knowledge.
To be more precise it asks if we have an adequate justification for anything we believe to be true. Philosophical
scepticism is sometimes described as hyperbolic scepticism as – unlike normal incredulity which simply arises from
‘everyday’ reasons for doubt (e.g., we doubt A’s claim he knows B is abroad, because we saw someone who looks just
like B moments ago) – it is willing to entertain any reason for doubt, no matter how fantastical or strange (e.g., the
brain in a vat hypothesis). While local scepticism applies philosophical scepticism to a limited range of knowledge
claims (e.g., about God or a mind-independent world), global scepticism applies it to all knowledge claims. In this
essay we will explore Descartes’s attempt – as described in his Mediations – to respond to global scepticism. We will
conclude that global scepticism can be resisted, but not in the ambitious way Descartes hoped.
After he announces that he is unwilling to accept any knowledge claim that isn’t free from doubt, Descartes begins
the Meditations by raising the Three Waves of Doubt (a series of sceptical arguments) which lead to global
scepticism. Of the three (illusion, dreaming, and the evil demon), Descartes admits that the evil demon hypothesis is
the most damaging as it seems to call both perception and thinking into doubt. However, despite this concern,
Descartes believes that even if the evil demon hypothesis is true, he knows for certain that he exists. This must be
true, because even if the evil demon is deceiving Descartes there must be an ‘I’ that is being deceived; the very fact
of doubting (a mode of thinking) is proof that he exists. I think, therefore I am. From this, Descartes goes on to
conclude that free from doubt and according to the ‘natural light’ of reason he must exist as a persistent thinking
thing.
This sounds like a promising rebuff to the sceptic but there is much in Descartes’ claim that is not free from doubt.
Firstly, as argued by Nietzsche, Descartes’ claim that he exists as a persistent thinking thing (i.e., as something that
exists over time) rests upon memory. However, without expelling the evil demon hypothesis Descartes has no reason
to trust his memory. Thus, even though we may be willing to concede that Descartes exists as a thinking thing, we
cannot say he persists over time, but only at the point in which he thinks.
However, it gets worse, because drawing on Hume, Descartes’ claim that he exists as a thing (i.e., as a mental
substance, a mind) also seems open to doubt. This is because this claim rests upon the assumption that thoughts
require a thinker, and it is not at all clear a priori or a posteriori how this is known. Firstly, if the proposition ‘thoughts
require a thinker’ was known a priori then it should be impossible to deny without falling into logical contradiction.
However, from a careful analysis of the meaning of the words in the proposition this isn’t the case (true, by
definition, a thinker requires thoughts, but thoughts don’t require a thinker). Therefore, it is not an a priori necessary
truth that thoughts require a thinker.
When we turn to the a posteriori, we can accept that Descartes has experienced thought but at no point is it clear
that he has experienced a mind, a mental substance that possess or causes these thoughts. As Hume convincingly
argues, Descartes has confused similarity between thoughts for a unified substance that possesses them (in the same
way that one might confuse similarity in the look and behaviour of individual birds moving in concert as a flock, as
the product of one unified substance). Descartes has only experienced a bundle of thoughts, not a mind or mental
substance that possesses them. This observation is further supported by introspection, which reveals an awareness
of thoughts, feelings, desires, etc., but at no point a ‘mind’, a ‘thinking thing’ that possess or causes them. Therefore,
Descartes does not have an adequate justification – neither a priori nor a posteriori – to claim knowledge of a thinker
simply based on thought.
Drawing all the previous material together, when we combine Hume and Nietzsche’s sceptical arguments, it would
seem that Descartes can only claim to know [at the point at which it is perceived] that a thought exists. This may be
enough to resist global scepticism, but before we consider this point any further, we shall turn to Descartes’s
arguments for God and physical objects.
Due to time constraints this essay will only consider Descartes’ trademark argument for the existence of God.
However, there is good reason to believe that both his cosmological and ontological argument rely on the ideas and
conclusions established by the trademark argument, and therefore if it is not sound then none of his arguments for
God’s existence are. Simply put, with his trademark argument, Descartes argues that GOD (the concept of God)
proves God exists, as God is the only being that could generate such a concept. At this point, we may protest and
