Dear Denis,

Thanks for some very cogent and relevant points. In relation to Leibniz I concede three caveats:

1. He probably did miss a few tricks and they are important issues to resolve.

2. He changed his mind significantly so I tend to read the Monadology as stand alone, even if some of the earlier pieces help see where he is coming from.

3. Our biggest problem is the multiple meanings of the important words we want to use - like change. I think Leibniz did quite a good job in steering round the problems but maybe not ideal and even if ideal certainly open to misconstruing if one has not seen his underlying agenda. Presumably translators may also introduce aberrations.

Ultimately what matters for me is a gist that can be reformulated in the context of modern physics and applied to the relation of the human subject to the world. The distinguishability of monads is tricky. Simon Saunders has written nicely on this in the context of current physics (monads being quantized modes). For familiar entities like photons, electrons or protons the monadic units of each type seem to be the same in terms of the ‘laws of God’ (to use Leibniz) that they obey but each unit is distinguishable by its ‘biography’ of in terms of its journey in the universe. Interestingly, where two electrons are truly indistinguishable (one coming from there and another that came from here and has come back here because it bounced off the one from there that it is indistinguishable from) they obey the rules of one thing (their histories co-interfere).

So distinguishability requires unique properties, but I am not sure that these are ‘qualities’ and certainly not qualitative properties in the usual sense. They can be ‘biographical properties’. Aggregates of monads will induce apperceptions in other monads that will include apparent qualities (or qualia) but these are not ‘qualities’ of the monads in the aggregate.

Leibniz attributes dominant monads to living things to explain the sense of a single ‘self’ with apperceptions. I actually think he is at least partly wrong about this (this is my key metaphysical interest). There is no need for it and it weakens his case by being unexplained. I am not clear that he attributes dominant monads to inanimate things – he does seem to indicate that aggregates like piles of stones are arbitrary. Nevertheless, I think modern physics does attribute something a bit like a dominant monad to an aggregate like a crystal or a billiard ball. In terms of group theory these structures have quantised modes that are more complex and variable than things like electrons. It brings back credence to the concept of forms – maybe Leibniz could half see why it should not be distained. These more complex monads are really what we are interested in in daily life and in relation to your further points.

My reading of Leibniz is that the biography of the monad, which is its perception and in a sense its very existence, is full of change, but that there is an aspect of the monad that remains the same (which is as you quote: there must be something which changes and something which remains unchanged). The perception/biography changes. What I see as that which does not change, or at least much less consistently, is a set of parameters within which the ‘laws of God’ apply to ‘steer’ that monad. For electrons and photons these are simple things like spin and charge value. For the acoustic phonons of large structures the parameters can be extremely complex.

So I see Leibniz as having no problem with ‘all is change from the third person perspective’ (just as all is apperception from the first) because this does not mean there is nothing that remains unchanged. What remains unchanged is a set of parameters defining the way the laws of change operate in that instance. In simple terms what stays the same is the pattern of change. The pattern perdures.

Would Leibniz have “agreed with Lonergan that if there is "change" there has to be a concrete unity of concrete data extending over some interval of time (however ephemeral), there has to be some difference between the data at the beginning and at the end of the interval, and this difference can be only partial for otherwise there would occur not a "change" but an annihilation and a new creation”?

My question here is for whom is this data? If this is data for the monad in question then there is a unity of data that forms the ‘biography of perception’ for the monad. But note that these are data about the universe, not about the monad. Moreover these are not 'changing data' in the sens eof the word change I am using. Change is the transition between data. Change is not 'given' to anything, it is what explains what is given and when it is. If you mean data for us wanting to track this monad through time then modern physics would say definitely no and I am not sure that Leibniz would think it relevant to our understanding of the monad being tracked.

My impression is that physicists are increasingly finding Leibniz in harmony with current thought. Leibniz’s view is verified in the broad sense that it is a framework that very happily accommodates the empirically confirmed features of quantum field theory that on the sort of basis that people like Rutherford operated on in the late nineteenth century seem ‘spooky’ and unexpected. ‘Interactions’ in modern physics look much more like ‘progress in harmony’ than anything billiard ballish. The complexity without parts fits perfectly with the indivisibility of a ‘quantum system’. Leibniz pre-empts any worries about a mind-body problem. I am tempted to think that it would be better to think of the monad as an instance of operation of certain parameterised natural laws rather than some notional entity being 'guided' by the 'laws of God'. However, I can see Leibniz's point here - his approach provides a good safeguard against relapsing into intuitive concepts of 'agents' and it works just as well.

You finish by saying that the notion of a thing is meticulously worked out by Lonergan in Chapter VIII  of  Insight but I am still unclear where he advances on Leibniz either in terms of providing a base for modern physics or elucidating things like the nature of the human self and its relation to the world. I am not sure I am drawn to try and find him in the library without a clearer trailer! Can you give a bullet point summary?

Jo