The phrase "assert either" is correct and usable in written English.
It can be used when discussing the act of stating or affirming one of two options or possibilities.
Example: "In the debate, the speaker chose to assert either the importance of climate change or the need for economic growth."
Alternatives: "claim either" or "declare either".
If the sufficiency doctrine were asserted either as a complete theory of justice or as a principle that trumps all competitors, it would definitely be problematic.
It settled for crumbs, asserting either that climate change was nature's way, or alleging that scientists climb on the climate bandwagon for research grants.
Many economists just dismissed the Japanese example, asserting either that it reflected very special circumstances — zombie banks!
Braun has never asserted, either in his case before the arbitrator or in his news conference last Friday, that the samples tested in a lab in Montreal bore any evidence of having been compromised.
The purpose of this paper is not to assert that either local or nonlocal genotypes are generally superior, but rather to simply suggest that circumstances exist under which the use of nonlocal genotypes may be a viable restoration option.
SBNation.com asserted, "If either Hackenberg or Ferguson gets hurt, and the other one stinks... if either Zach Zwinak or Bill Belton (who missed four games last year) gets hurt... if basically any linemen get hurt (and linemen often get hurt)... this house of cards comes tumbling down".
Hernández Colón asserted that either statehood or independence would result in the island's economic and political ruin.
Many Nazis, as Stuart asserts, "were either vegetarian or interested in related issues" because they, like the Stalinists of the same period, believed they were ushering in a new age, answering to a higher law.
It is this definition of continuity that figures in Aristotle's demonstration of what has come to be known as the isomorphism thesis, which asserts that either magnitude, time and motion are all continuous, or they are all discrete.
It is unclear how solar particles affect rates of radioactive decay, but Prof Jenkins asserts that "either neutrinos are affecting the decay rate or perhaps an unknown particle is".
