WHAT IS LOGIC?
Logic may be defined as the science of reasoning. However, this is not to
suggest that logic is an empirical (i.e., experimental or observational) science like
physics, biology, or psychology. Rather, logic is a non-empirical science like
mathematics. Also, in saying that logic is the science of reasoning, we do not mean
that it is concerned with the actual mental (or physical) process employed by a
thinking entity when it is reasoning. The investigation of the actual reasoning process falls more appropriately within the province of psychology, neurophysiology, or
Even if these empirical disciplines were considerably more advanced than
they presently are, the most they could disclose is the exact process that goes on in
a being's head when he or she (or it) is reasoning. They could not, however, tell us
whether the being is reasoning correctly or incorrectly.
Distinguishing correct reasoning from incorrect reasoning is the task of logic.
INFERENCES AND ARGUMENTS
Reasoning is a special mental activity called inferring, what can also be called
making (or performing) inferences. The following is a useful and simple definition
of the word ‘infer’.
To infer is to draw conclusions from premises.
In place of word ‘premises’, you can also put: ‘data’, ‘information’, ‘facts’.
Examples of Inferences:
You see smoke and infer that there is a fire.
You count 19 persons in a group that originally had 20, and you infer
that someone is missing.
Note carefully the difference between ‘infer’ and ‘imply’, which are
sometimes confused. We infer the fire on the basis of the smoke, but we do not
imply the fire. On the other hand, the smoke implies the fire, but it does not infer
the fire. The word ‘infer’ is not equivalent to the word ‘imply’, nor is it equivalent
The reasoning process may be thought of as beginning with input (premises,
data, etc.) and producing output (conclusions). In each specific case of drawing
(inferring) a conclusion C from premises P1, P2, P3, ..., the details of the actual
mental process (how the "gears" work) is not the proper concern of logic, but of
psychology or neurophysiology. The proper concern of logic is whether the inference of C on the basis of P1, P2, P3, ... is warranted (correct).
Inferences are made on the basis of various sorts of things – data, facts, information, states of affairs. In order to simplify the investigation of reasoning, logic