Looking for a term like "fundamentalism", but without a religious connotation [closed]

Solution 1:

Those who want to return to the 'foundations' of their particular ideology or concept or system practice fundamentalism; those who return to the roots or radices (radix is Latin for 'root', cf. English radish, eradicate) practice radicalism. There often isn't much of a difference between the two.

As you say, fundamentalism is more often used to describe religious movements, but this is by no means exclusively so. Either word will do.

Solution 2:

How about absolutism?

From Dictionary.com:

absolutism: any theory holding that values, principles, etc., are absolute and not relative, dependent, or changeable.

absolute: something that is not dependent upon external conditions for existence or for its specific nature, size, etc. (opposed to relative)

the absolute: something that is free from any restriction or condition / something that is independent of some or all relations

A believer in absolutism and absolutes is an absolutist.

Solution 3:

In comments, FumbleFingers answered:

OED dogmatism - the tendency to lay down principles as undeniably true, without consideration of evidence or the opinions of others. There are plenty of written instances of dogmatic economists, for example, and I doubt many of them imply any connection to religion.