sceptic

As a noun sceptic

is someone who is undecided as to what is true and enquires after facts.

As a verb speculate is

to think, meditate or reflect on a subject; to consider, to deliberate or cogitate.

As a noun sceptic

is someone who is undecided as to what is true and enquires after facts.

As an adjective speculative is

.

As nouns the difference between taxonomy and sceptic

is that taxonomy is the science or the technique used to make a classification while sceptic is someone who is undecided as to what is true and enquires after facts.