1.
A Priori Knowledge – “Some ideas are true independent
of experience”. Whilst rationalists did not deny
that the senses give us important information about the world,
they did not consider them to be the sole means of knowledge.
In fact, they quite often thought that the senses mislead us.
For this reason, they argued that knowledge which is independent
of experience must be more trustworthy because it has less to
do with the senses. Such ideas they called a priori, which is
a Latin phrase meaning “prior to” or “before”
– experience, that is. Examples of such knowledge include:
a. Mathematical propositions (2 + 2 = 4).
b. Things which are true by definition (all
bachelors are unmarried).
c. Self-evident truths (such as “I think
therefore I am” or “God exists”).
2.
Innate Ideas – “Some ideas are present from birth”.
Amongst those ideas which do not require the proof or
suggestion of sense experience are concepts which are present
from birth. These ideas – which are called innate –
can theoretically be discovered or ‘brought out’ (the
original meaning of the word “education”) from within
the mind of each individual. So, for example, one of Descartes’
arguments for the existence of God is that the idea is present
in the mind from birth, left there almost as if an artist had
signed his work or left a trademark.
3.
Logical Necessity – “Some things cannot be conceived
of as otherwise”. Another important idea for rationalists
is that of necessity. Although we may use the word everyday, the
rationalists actually meant something very specific by it. So,
for instance, we might say something like, “In order to
pass your exams you have to study hard”. However, in reality,
there are lots of ways you might pass your exams: you may have
a natural talent for learning so that you don’t have to
work hard (it just sticks); you may be lucky; you may bribe an
examiner – or cheat. However, if we were to say something
like, “In order to have 3 things you have to have more than
2 things,” then we are approaching more what the rationalists
meant by the term. To distinguish between these two uses, philosophers
generally call the first sort – passing your exams –
“empirical necessity” (it could be otherwise); the
latter sort (having 4 things) is called logical necessity. So,
if we can prove that something is true because “it could
not be otherwise”, then we have achieved logical necessity
and an absolute degree of certainty. The goal for rationalists
was therefore to find those “logical necessities”
which would help us find certainty in the world and answer those
difficult moral, religious and metaphysical questions that interest
us so much.
