I read a surprisingly enjoyable book you might like on the history of double entry accounting, developed in the markets of Venice in the 16th century as Arabic numerals began replacing Roman numerals for their easier arithmetic. More thorough month to month bookkeeping of profits and losses was a precursor to anyone investing their own money in someone else’s business. Before that it was just Royal families funding risky excursions.

The book is “Double Entry” by Jane Gleeson-White

A gear is equivalent to a wheel with a large coefficient of friction. Is there a particular reason you consider it to be a separate invention?

Gear drives don't work with flat wheels, you have to have belts or elaborate movable axles to keep them pressured together.

Metal gears are also considerably difficult to make reliability. I'd be interested in a history of the gear.

I'm sure it's more about infinite lever/ratio than the teeth.

invention (n): the action of inventing something, typically a process or device.

device (n): a thing made or adapted for a particular purpose

The purpose is different.

Sure; I'm arguing that the leap necessary between wheels and gears isn't really all that huge. A gear is basically just a wheel–regardless of whether you think it's a separate invention or not it's not really that impressive as going from nothing to the wheel.

A gear is a lever which uses a wheel to apply continuous leverage - I would say using wheels as force multipliers is a considerable jump in cleverness than just using them to roll around

Gears provide mechanical advantage -- i.e. gear ratio.

So do two wheels of different sizes.

My vote is for moveable type: Suddenly Bibles became cheap and people could question the structure of the church. News papers came and people could debate the structure of the state. Scientific books and journals.

I recommend a podcast from the World Service called "50 Things that Made the modern Economy". They are short (8min) episodes, by Tim Harford (the Undercover Economist).

Some of them are the obvious, but there are also many less so items that have had surprising impacts. Obviously they are short, so not lots of details, but they always cite their sources at the end if you are inspired to read more.

Wow that sounds like it would be a great conversation to be a part of. Why do you put joint stock corporations as number one though ?

One of the nice things about marrying someone from a very different background yet with many shared interests is that life together can be really fun. That particular conversation (what are the most important inventions) probably spanned more than a decade. It was not the only such. Sometimes a topic would go into abeyance and then one of us would read something that would reignite the topic for a while.

I don't think either of us would have ranked the JSC #1, but in the top 5 or so, sure. It's not like one can definitively generate a proper ranking, but some things are clearly top 25 but not top 10, for example.

We've been debating this recently, and I'm curious your take: is a corporation a form of artificial intelligence?

No, I consider a corporation simply to be a machine operated by people.

I do find it disturbing that if you run my over while driving a car you, not the car, is punished while if a corporation knowingly poisons people the people “driving” it are rarely punished at all.

you might appreciate Charles Stross' take on the situation

http://www.antipope.org/charlie/blog-static/2010/12/invaders...

How can you include those but not insurance?

Insurance is essentially gambling, which has existed since ancient times, backed by a too-big-to-fail institution, which is made possible in modernity by the joint stock corporation.

Lloyds was historically structured as a partnership, specificity not a limited liability structure.

What is the fifth one?

Writing, iirc.