In the 19th century, the theory of natural selection was considered heretical.

However, theories of a possible assassination were considered seriously by some.

Other theories can be considered in terms of the security dilemma.

The theory is considered viable and remains an active topic in the physics community.

However, this theory is considered to be wrong for the following reasons:

This theory is now generally considered obsolete in academic circles.

Of course such a theory is considered by many to be, more or less, a myth.

"As I noted before, basic theory cannot be considered reliable regarding such matters."

This theory is also generally considered as a very unlikely purpose of the voyages.

However, this theory is not currently considered to have much supporting evidence.