I have a question about this video regarding Leibniz, monads and interaction:


at 33:27.

On the one hand, Anthony Quinton says that a monad has no interaction with other monads... each monad acts according to its own history and internal program.

But he also says that monads are aware of other monads... If this is the case, won't the monads observation of other monads have an impact on the program it runs?

I mean, to avoid causality, a monad's observations of other monads has no impact on its actions. But what justification does Leibniz have to forbid this? It seems ad-hoc. A monad observes other monads, but those observations cannot act as an input to its program?

EDIT: Putting it more simply, if a monad observes other monads doesn't that mean that there is interaction between the two? What does it mean for one monad to be aware of another without some type of causation?

  • good question, but not sure what "ad hoc" has to do with philosophy
    – user28117
    Aug 14, 2017 at 16:29
  • i suppose that if you're not an ontological naturalist, philosophy might be involved in explaining some "things" in place of scientific study. but even supposing leibniz is committed to the supernatural, it's not for me obvious that his monadology should avoid ad hoc justifications
    – user28117
    Aug 14, 2017 at 16:36
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    ok, cool. anyway, i may be completely wrong headed there, in which case i apologise! i suppose what i mean is just that i'm unused to arguing that given if A then B, then less likely C, and if B then C, so not A. likely because that sorta reasoning, if legit, seems implicit in most literature
    – user28117
    Aug 14, 2017 at 16:38
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    I feel, along with Schrodinger, who hated the blasted things, that these monads are an unworkable idea, as well as being terrifying. Yet also that they capture something of the truth. Brilliant philosophers are often wrong when they speculate, but rarely so badly that their idea don't have merit.
    – user20253
    Aug 14, 2017 at 18:04
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    If monads were universes then you've got one notion of the multiverse; after all in a multiverse, each is causally disconnected from each other, so there is no cause/effect; yet there are physicists who claim they are there...it all hinges upon what you mean by observation. Aug 14, 2017 at 20:43

2 Answers 2


@Conifold, what do you mean by not being able to act "arbitrarily"? Arbitrariness is a fuzzy concept for me, but in this context it sounds like freedom. But Leibniz's harmony is not supposed to preclude freedom of rational souls, whose actions are to be rewarded and punished in the city of god (Monadology, article 90). Would you clarify? Thanks.

As to @Ameet Sharma's original question, monads represent the entire universe in themselves (Monadology, article 60). Thus, their observation of other monads is an internal observation, and their interaction consists of an ideal influence which is rendered effective by God through pre-established harmony (Monadology, article 51). Hope this is helpful.


For me to understand Leibniz about your confusion lies in his definition of "interaction", "causation". His "interaction" is meant to be a monad changes another monad's internal pre-programmed code, is not to be meant as physical action-reaction like interaction. Of course he didn't deny "if I hit you then I interact with you" expressed in common language, what he denies is simply "if I hit you then I cause your pain" in its literal sense. Of course ultimately I'm the source of your pain, but your pain is nothing but an internal monadic consciousness whose business logic code already pre-established during its creation. Any outside influence is just a stimulus, not real cause as confused by mundane language.

In summary for Leibniz, there's always a clear ontological boundary between monads as they're clearly defined simple substance. Under this rational view, monad is ethically responsible to itself as direct first main cause, any outside "interactions" are simply stimuli as unit tests...


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