Secular alternative to "doubting Thomas"

Question

When looking at this question, the phrase "doubting Thomas" popped into my head as a potential answer. That in turn led me to question the origin of the phrase, which I discovered comes from the Apostle Thomas being skeptical of Christ's resurrection.

After learning that the phrase "doubting Thomas" has a religious origin, I'm curious...Does a "colorful*" expression that is secular in nature exist to describe a skeptical person, and if so, what is it?

Obligatory frame sentence:

That guy never believes anything without proof; he's a(n) _____________.

*By "colorful," I mean a bit more inventive/expressive than simply "skeptic," "doubter," etc.

Edit to address smci's comment: I prefer an existing and reasonably common expression; however, I will accept an uncommon or newly created expression that would be widely understood if there seems to be a consensus that a common one does not exist.

Edit to address MετάEd's comment: To further clarify and keep the question within the appropriate scope, I am not looking to compile a list of similar expressions. I'd like to identify the most common, secular expression that closely matches "doubting Thomas" in meaning and usage.

***To preserve the validity of answers that suggested coining new expressions, note that several users have asserted the lack of an expression that meets the criteria I've laid out.

Answer 1

That guy never believes anything without proof, he’s a real show-me guy.

Google finds a lot of examples of this being used in, what seems to me, the sense you are looking for and it is also easy to understand from context even if one hasn’t encountered it before.

I am very much a “show me” guy and no amount of claims over the phone is going to convince me.

I'm a "science" kind of guy, a "show-me" guy, someone who tends to need some proof about claims I find questionable.

He was very much a "show me" guy. When he heard that magnesium would burn underwater he took a five-gallon coffee can to work and filled it with magnesium chips from the shop floor. He put the can in the driveway at home and filled it with water,

My only reservation with this is that people do tend to put the phrase in inverted commas when they write it, which seems to set it apart as though they don't quite feel it is 'proper' language.

Answer 2

As an alternative view to your statement I'd say that the expression doubting Thomas has been secularised in the English language from the start since there is no mentioning, as in other languages, of the "Saint" Thomas.

In French: Saint Thomas : "Je suis comme Saint Thomas, je ne crois que ce que je vois"

In Italian: San Tommaso. "Fare come San Tommaso"

In Spanish: Santo Tomás: "Ver para creer, como Santo Tomás."

Answer 3

What about

"That guy never believes anything without proof; he's from Missouri/a Missourian".

Someone "from Missouri" is someone who always needs proof, who always doubts. I think this option has the exact meaning you desire, and it also seems to satisfy the criterion of being "colourful".

(McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.)

• And it's well established and recognized, at least in the United States, where Missouri is nicknamed "The Show Me State". It's definitely secular, and you can find (one version of) it's origin/popularization here.

Answer 4

If someone doubts something, they are sceptical and therefore a sceptic

(Skeptical/skeptic in US English)

Answer 5

I couldn't find anything from researching it (well not anything colourful).

So I decided to invent a term... only to find it has actually been used elsewhere. Makes me feel pretty noble ;)

Anyway this is my offering...

A "Septic Sceptic"

The connotations being a person that so doubts everything they make their life a misery of indecision and unbelief, and possibally also infect those around them with this contaminated view point.

Septic

1: of, relating to, or causing putrefaction
Merriam Webster

I couldn't find a defintion of the term in any dictionaries but I have found some examples of the term being used: -

"Aunt Maud's perceptions were somehow septic. A septic sceptic."

Blue Voyage: A Novel, Conrad Aiken, 1927 (ref)

and here is another more recent example: -

"Deborah laughed. 'You're impossible. Even you admitted that of all the psychics you investigated over the years, Oliver Sangster is the only one who cast doubt into your suspicious mind... So, how did he predict the bus crash? Come on Septic Sceptic. Explain.' "

Whispers of the Dead, Anthony Hulse, 2014 (ref)

Answer 6

Descartes is the modern philosopher who is most associated with doubt, quoting him:

The first [principle] was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgment than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.

Thus, the word Cartesian can qualify someone who doubts by nature and requires a proof of any assertion — although compared to Thomas, he requires a logical proof and distrusts his senses more than his brains. Depending on the context and what you want to achieve, you might even coin a doubting Descartes, which will insist on secularism even more thanks to its parallelism to doubting Thomas.

A British alternative to Descartes, as you point yourself, is Hume, and indeed in Oxford dictionaries the adjective Humean is listed with the relevant example sentence:

Relating to or characteristic of the Scottish philosopher, economist, and historian David Hume or his ideas:

a critic of Humean scepticism

Answer 7

"That guy never believes anything without proof; he's an empiricist," one with "The view that experience, especially of the senses, is the only source of knowledge."

Answer 8

Blaise Pascal names sceptics Pyrrhonists in his Pensées, which I find a rather colorful solution, albeit probably with a stronger meaning than simply "not believing what one has not seen": indeed pyrrhonists seem to doubt even of what they do see.

Answer 9

I'm going to make the case for Doubting Thomas, on the grounds that its religions origin is irrelevant (to pretty much everyone). Etymology is not meaning.

This type of word/phrase is an allusion. Allusions are popular in English, and the Bible, as a source of many stories that are widely known, is a popular choice for allusion. Another choice is Shakespeare. In a few decades, maybe Harry Potter will be people's choice of allusion, and you might hear a teacher say

You're a real Hermione Granger

to a student who's memorized every school textbook.

Here is a list of some commonly-used allusions. Note that some of them are religious in origin, but the source religion is not Christianity (example: erotic is from the god of love Eros).

Doubting Thomas is a character in a story. Whether the story is true or not doesn't matter as much as people understanding your allusion. This is different from, say, trying to avoid religious sentiment when you don't intend it. For example, some people feel compelled to say something when another person sneezes, but they don't want to say "Bless you". In that case, a non-prayer-related interjection is required, such as "gesundheit". In this case, Doubting Thomas doesn't convey any notions of prayer, or belief, or anything. It does convey the notion that Thomas was wrong to doubt, which may be something to avoid.

It should also be noted that lots of common words and expressions are religious in origin, such as "good-bye", "damn", "hellish", etc. I think most atheists wouldn't blink at saying something like "Damn, today's shift at work was hellish. I can't wait to say good-bye to that place."

Answer 10

William Safire's "Nattering nabobs of negativism" could be applied.

Answer 11

Empiricist

Empiricism is a theory that states that knowledge comes only or primarily from sensory experience.

Thomas did not believe the other apostles because he had not seen it with his own eyes, thus he was an empiricist.

Or, as in your example:

That guy never believes anything without proof; he's an empiricist.

Answer 12

Colloquial British: "Negative Nancy"

"Negative Nancy" is perjorative, but "Doubting Thomas" also is traditionally; "Stop being such a 'Doubting Thomas'". The switch to being an expression of intelligent skepticism is very recent.

Both are generally used when someone is questioning the feasibility of an idea, whereas appelations ike "Debbie Downer" are more about emotional mood.