Why is the concept of continents open to interpretation?

Question

Why is the concept of continents open to interpretation?

Answer 1

Size can be a problem.  If it is big enough an island is called a continent.  Australia is sometimes referred to as the island continent.  

Continuity.  Eurasia is a one land mass divided by a not very high (and very old) mountain range.  We count it as two, the division is not quite arbitrary but it follows no rules.  AS part of the same continuous land mass India is referred to as the subcontinent (newly joined to the rest of Asia).

South of Texas, in all of Latin America, the Americas are considered one continent,  people in the U.S.are taught it is  2 continents, North and South, connected by a small (and very young) land bridge, Central America.

So, it is subject to interpretation, and the continents can be divided according to language, geology, geography or cultural traditions.  All of these method are used, none consistently.

Answer 2

Um... well, certainly Europe and Asia are part of one land mass (Eurasia), so to define continents as contiguous land masses would require reconsideration of those two continents as separate.  Also, how large must a land mass be to be considered a continent?  Greenland is quite large for an island, don't you think?  And where do islands fit in?  Also, does any land connection between continents disqualify them?  North America and South America were connected prior to the Panama Canal.  And North America and Asia were connected by Alaska when the oceans were lower.  So the line between continents can blur as ocean levels change.  They certainly blur as tectonic plates shift over long periods of time, as today's continents were once connected to one another.  So all of these are reasons why the idea of "continents" can be brought into question.