Word for 'believing there is always a simple solution'

Question

What is the word for a person who thinks there is always a simple solution to any given problem?

I have heard this term used before in an intellectual debate in the past, but cannot remember what it is.

The word itself may not have been used to actually refer to a type of person, but to the belief itself (I don't remember this detail either). It also may have been a noun or an adjective (probably a noun, imo), for all I remember.

Addendum 1: in the debate, the belief (or the person holding the belief) was presented as silly, a bit irrational, unrealistic

Addendum 2: the problems the debate was focused on primarily were more down-to-earth in their nature, though global problems were not excluded per se.

Answer 1

A good match should be simplistic — ODO

adjective Treating complex issues and problems as if they were much simpler than they really are: "simplistic solutions"

Answer 2

Naive is associated with meanings you are looking for, but is maybe more strongly asserting that the simplicity of the person is due to their ignorance:

(Of a person or action) showing a lack of experience, wisdom, or judgement

(Of a person) natural and unaffected; innocent

Of or denoting art produced in a style which deliberately rejects sophisticated artistic techniques and has a bold directness resembling a child’s work, typically in bright colours with little or no perspective.

(Oxford dict)

Naif (or naïf) is the associated noun.

Answer 3

How about Reductionism

Particularly the second definition given:

the practice of simplifying a complex idea, issue, condition, or the like, especially to the point of minimizing, obscuring, or distorting it.

Answer 4

Facile - MW

too simple : not showing enough thought or effort

Maybe more negative/insulting than what you were looking for.

Answer 5

How about,

Unsophisticated

adjective
1. not sophisticated; simple; artless.
2. without complexity or refinements: a relatively unsophisticated mechanism.

Ref dictionary.com

Answer 6

Idealism — ODO

noun 1. The unrealistic belief in or pursuit of perfection

"We learned about the three ‘major’ sets of political beliefs - idealism, liberalism and realism."

Idealist — ODO

noun 1. A person who is guided more by ideals than by practical considerations
"he came to power with the reputation of a left-wing idealist"

Idealistic — Vocabulary

When you're idealistic, you dream of perfection, whether in yourself or other people. For example, you might have the idealistic goal of bringing an end to childhood poverty in the world.

The adjective idealistic describes someone whose plans or goals of helping others are lofty, grand, and possibly unrealistic. Do you think world peace is within reach? You're idealistic. If your vision of the world is idealistic, you believe all problems can be solved and that all people can reach their full potential. Idealistic comes from the Greek idea, or "ideal prototype."

Answer 7

In the context of a debate I might expect to hear someone use Sophomoric to describe someone who in your first addendum.

from MW:

conceited and overconfident of knowledge but poorly informed and immature

Answer 8

A simplicist? simplism being "the act or an instance of oversimplifying; especially : the reduction of a problem to a false simplicity by ignoring complicating factors" Merriam Webster

Answer 9

optimistic

1.)
disposed to take a favorable view of events or conditions and to expect the most favorable outcome.
_{-Dictionary.com}

Answer 10

It doesn't quite match, but "populist" might be close to what you are looking for. To call something or someone "populist" is to imply that their ideas are simplistic and calculated to appeal to many people, even though a thoughtful or detailed analysis will show that they are flawed. An example is blaming economic problems on an unpopular ethnic group, and suggesting that the solution is therefore to get rid of that group.

Answer 11

Parsimonious or parsimony in philosophy is the belief that, all things equal, the simplest solution (I.e the fewest entities / physical things) is the best solution ( in-line with Occam's razor).

Stanford encyclopedia of philosophy

Ontological simplicity, or parsimony, measures the number of kinds of entities postulated by the theory.