I don't understand how Berkeley justifies existence of other minds in his system. Is it something that he takes for granted? Because, his position seems very close to that of a solipsist except for acknowledgement of other minds.

You'll perceive human bodies, which are physical objects(which in turn are nothing but "bundles of ideas") but then how can you say that there is this thing called mind that sits inside these bodies - which are bundles of ideas?

Does berkeley acknowledge this problem in his work. how does he tackle the threat of reduction to solipsism?

This issue is addressed in Berkeley's Treatise Concerning the Principles of Human Knowledge, especially 145 and 148, and there is some disagreement as to what the nature of his argument is. Some take it to be an argument by analogy: we see bodies and behaviors similar to our own out there, and infer that there is a mind behind it. Others point out that the analogy, if any, appears in Berkeley's conclusions rather than in his inference steps. Instead, we just infer "other spirits" from "their operations", some "collections of ideas" lead us to believe that there is a cause behind them, and that cause is a mind. If so, this is similar in spirit to the cosmological argument for the existence of God, where the existence of the first cause is first established, and then it is identified with God by (what we would now call) an inference to the best explanation. Indeed, when it comes to God's mind the cosmological argument is part of Berkeley's reasoning. For the analogy argument thesis see Urmson's book, and for its criticism, and defense of the causal argument see Falkenstein, Berkeley's Argument for Other Minds. Here are the source passages:

"From what hath been said, it is plain that we cannot know the existence of other spirits, otherwise than by their operations, or the ideas by them excited in us. I perceive several motions, changes, and combinations of ideas, that inform me there are certain particular agents like my self, which accompany them, and concur in their production. Hence the knowledge I have of other spirits is not immediate, as is the knowledge of my ideas; but depending on the intervention of ideas, by me referred to agents or spirits distinct from my self, as effects or concomitant signs". [Principles 145]

"A human spirit or person is not perceived by sense, as not being an idea; when therefore we see the colour, size, figure, and motions of a man, we perceive only certain sensations or ideas excited in our own minds: and these being exhibited to our view in sundry distinct collections, serve to mark out unto us the existence of finite and created spirits like our selves. Hence it is plain, we do not see a man, if by man is meant that which lives, moves, perceives, and thinks as we do: but only such a certain collection of ideas, as directs us to think there is a distinct principle of thought and motion like to our selves, accompanying and represented by". [Principles 148]

The wording of Principles 145 is somewhat peculiar, especially from the point of view of the causal argument. The finite spirits only "accompany and concur in production" rather than "cause". It is an indication of the fact that for Berkeley God is the ultimate cause of all the commotion. In which case, their existence is not exactly inferred by best explanation to the cause. Berkeley has to deal with this also for the purposes of theodicy, for putting God too close to the causing would make him responsible for the resulting evil. In the Dialogues, Philonus explains:

"I have nowhere said that God is the only agent who produces all the motions in bodies. It is true, I have denied there are any other agents beside spirits: but this is very consistent with allowing to thinking rational beings, in the production of motions, the use of limited powers, ultimately indeed derived from God, but immediately under the direction of their own wills, which is sufficient to entitle them to all the guilt of their actions."

This turns theodicy into a peculiar argument for the existence of other minds (other than God's), if not for them God would have to be convicted of causing the apparent mayhem.

This issue is clarified by understanding Berkeley's living understanding of his project. Under the principle that ideas become ridiculous when separated from living interests.

Berkeley's motivation is to show that reducing knowledge to the subhuman things is impossible. He repeatedly affirms that he is in favor of the common sense attitude, and repeatedly insists that "An Irish man can not attain to these truths," meaning the fantastic ideas of the Metaphysical or Philosophic Materialists who project the intellect into the things. Berkeley takes the side of nous, the higher part of the soul. He argues against episteme, mathematical calculative thinking. His motivation is to show that morality can be derived from the things by nous or reasonableness. God "speaks" to humans through these things. The whole motivation of his system is to say, one can not build up from the subhuman things, mathematically. Rather, one must admit the things higher than man, the moral principles.

Therefore, one can see that he must, not merely admit grudgingly, but aver steadfastly, the reality of the human agent and the community of "persons."

Berkeley and other minds - the basic problem

The 'problem of other minds' confronts many philosophical theories for different reasons and with different responses. So how does it arise for Berkeley and what arguments does he deploy in connection with it ?

A common approach to 'other minds' - to justify belief in or establish knowledge of their existence - is to use an argument from analogy as set out below. Berkeley's principal reliance seems in contrast to be a causal argument.

The argument from analogy

Knowledge of other minds poses special problems for Berkeley. Besides taking the bodies of other persons to be mere collections of
ideas in my mind, he insisted that I cannot have any idea of the mind or
spirit of another. For him, ideas are passive and inert and therefore totally
inadequate to convey a likeness of an active being, spirit, or mind (Principles 27). Lacking ideas of minds, Berkeley supposed that I can still come
to know of my own mind through a peculiar non-sensory capacity, which
he called "inward feeling or reflection" (Principles 89), and that I can
deduce the existence of God by reflecting that only a supremely wise and
beneficent spirit could produce the variety, order and coherence exhibited
in my ideas of reality (Principles 30). But while he prided himself on having
provided a clearer and more certain proof of the existence of a divine spirit
than any other in history (Dialogues II 212-213), he had little to say about
why I should suppose that other minds like myself exist.

Despite these difficulties knowledge of other minds is not the sort of
insurmountable problem, embarrassment, or scandal commentators on
Berkeley often make it out to be. He does have an argument for affirming
the existence of other minds, though it is one which has been widely
misinterpreted and unjustly criticised. In what follows I will present this
argument as I believe Berkeley intended it and I will try to show that
considered from an internal perspective - a perspective which grants the
basic tenets of Berkeley's immaterialism - it is both coherent and plausible. My point will be, therefore, that the philosophy of immaterialism has
no special problem with other minds and that one can be an immaterialist
without having to be a sceptic about their existence.

The primary locus for Berkeley's views on other minds is Principles 145:

From what hath been said, it is plain that we cannot know the existence of
other spirits, otherwise than by their operations, or the ideas by them excited
in us. I perceive several motions, changes, and combinations of ideas, that
inform me there are certain particular agents like my self, which accompany
them, and concur in their production. Hence the knowledge I have of other
spirits is not immediate, as is the knowledge of my ideas; but depending on
the intervention of ideas, by me referred to agents or spirits distinct from my
self, as effects or concomitant signs.

It has frequently been maintained that the argument of this passage is one from analogy. Supposedly, Berkeley appeals to a certain resemblance be
tween our ideas of our own bodies and our ideas of other bodies and from
this he infers that other minds exist. But the argument for other minds
that is contained in this passage is not an argument from analogy. Berkeley
does not say that we infer the existence of other spirits from a resemblance
between their bodies and our own body or even from a resemblance between
their operations and our own operations. He simply says that we infer the
existence of other spirits "from their operations." There are no premises
affirming likeness or similarity or resemblance between these operations
and any other. Berkeley does indeed note that these finite spirits, whose
existence he infers, are "like myself." But this is stated as a conclusion, not
as a premise.
A similar point can be made about Principles 148 which, in the process
of explaining what it is to "see" God, digresses to make the following
comment on what it is to "see" other minds.

A human spirit or person is not perceived by sense, as not being an idea; when
therefore we see the colour, size, figure, and motions of a man, we perceive
only certain sensations or ideas excited in our own minds: and these being
exhibited to our view in sundry distinct collections, serve to mark out unto us
the existence of finite and created spirits like our selves. Hence it is plain, we
do not see a man, if by man is meant that which lives, moves, perceives, and
thinks as we do: but only such a certain collection of ideas, as directs us to
think there is a distinct principle of thought and motion like to our selves,
accompanying and represented by it.

Here again Berkeley concludes the existence of certain finite and created
spirits "like" ourselves, but the premises for this conclusion make no
reference to any likeness or analogy. When we see a person we experience
certain sensations or ideas exhibited in sundry distinct collections. There
is no remark that these collections resemble any other collection. It is
simply stated that our experience of certain collections of ideas directs us
to think that there is a distinct "principle" of thought and motion (like to
ourselves) which serves as their cause. (Lorne Falkenstein, 'Berkeley's Argument for Other Minds', History of Philosophy Quarterly, Vol. 7, No. 4 (Oct., 1990), pp. 431-440: 431-2.)

Counter-argument answered

There is, however, one important use which Berkeley does make of
analogy when discussing other minds: He notes that it is only through
reference to my own case that I am able to form some notion or representation of another spirit.
as we conceive the ideas that are in the minds of other spirits by means of our
own, which we suppose to be resemblances of them: so we know other spirits
by means of our own soul, which in that sense is the image or idea of them, it
having a like respect to other spirits, that blueness or heat by me perceived
hath to those ideas perceived by another. [Principles 140]
But note that Berkeley is not here explaining how we come to know that
other minds exist. He is explaining how we can be able to represent other
minds in thought. Here indeed analogy is at play. We have some "notion"
of our own minds through an extra-sensory, inner intuition and we use this
notion as a model of what other minds must be like?as, if you will, the
"image or idea" of other minds. But to use analogy in order to imagine or
form a notion of other spirits is one thing, to establish the actual existence
of such imagined entities is quite another. Berkeley affirms the existence
of other spirits from their effects, not from an analogy with his own case. (Falkenstein: 434.)

The argument from causation

Causation is indeed the key.

While Principles 145 and 148 do not appeal to analogy they do appeal to
the cause-effect relation. In Principles 145 Berkeley refers to the ideas I
have as "effects" which are "excited in us" by other spirits or "agents" which
"concur in their production." And in Principles 148 these other spirits are
described as "principles" of thought and motion. The idea is clearly that
from the changes in my ideas?particularly those which I take to be
expressions of thoughts or motions of a body? I go on to infer the existence
of a particular cause responsible for those changes. This cause I then take
to be another spirit, incidentally like myself. Another spirit because, as
Berkeley frequently insists, spirit just is the only possible cause.3 And like
myself because, presumably, the effects I witness are limited to the
thoughts and emotions of some one animated body (hence the spirit is
another finite spirit) and because these thoughts and motions evidence a
degree of rationality (hence the spirit is another intelligent spirit).
Thus I infer the existence of other spirits, not from the resemblance of their
bodies to my own, such resemblance being totally unnecessary, but "from
their operations"?operations which, for Berkeley, reduce to alterations,
motions and combinations of ideas.

Berkeley's argument for other minds is therefore a casual argument and
not an argument from analogy. This should not be surprising. Causal
argumentation does, after all, play a very large role in his thought. In
Dialogues II he has his partisan, Philonous, declare:

That from a cause, effect, operation, sign, or other circumstance, there may
reasonably be inferred the existence of a thing not immediately perceived, and
that it were absurd for any man to argue against the existence of that thing,
from his having no direct and positive notion of it, I freely own. [223]

and in the Principles arguments from effects to causes are used to prove
such basic doctrines as that spirit must exist as well as ideas (Principles
26), that some other spirit besides myself must exist (Principles 29), and
that God exists (Principles 30). Berkeley's argument for other minds is
merely the last in a series of casual arguments used to establish increasingly specific claims about the metaphysical principles and agencies pro
ducing our ideas. To read him as appealing instead to analogy is possible
only by spuriously interpolating premises in no way contained in the text
of his arguments and by illegitimately ignoring the very explicit causal
language in which those arguments are presented. ((Falkenstein: 432-3.)

I have already exposed to this problem during my Philosophical journey.

There are very important questions:

• Is it possible that there's nothing but God and me?. Is it a solipsism?.




• Could it be a solipsism but for many spirits?, Each mind passes through a specific clear, orderly, coherent and solipsistic dream?. Or it's one dream, takes place in the same time for many minds?.

If we can answer the question: what creation means for God?.It is then so easy to expect what type of world, or worlds are created.

Hindu Philosophy says it is a pastime, sport for God, they call it Lila.

For God to have more sport, pastime, is it pereferable for creation to be a uni-solipsism or many-solipsism or one dream for many souls (minds)?.

Thus we have four possibilities:

1- There's only one world with one mind only=uni-solipsism. That means less pastime, sport for God.

2- There are many worlds, each world having only one mind=many-solipsism.
That means more pastime, sport for God.

3- There's one world having many minds. This means more and more pastime, sport for God.

4- There are many worlds, each world having many minds. This means the highest pastime, sport for God.

But, how did Berkeley justify the existence of other minds?, We can quote from his works as follows:

For Berkeley, we have no direct 'idea' of spirits, albeit we have good reason to believe in the existence of other spirits, for their existence explains the purposeful regularities we find in experience.[21] ("It is plain that we cannot know the existence of other spirits otherwise than by their operations, or the ideas by them excited in us", Dialogues #145). This is the solution that Berkeley offers to the problem of other minds.

So, Subjective Idealism=clear, orderly, coherent Dream.

Justifying other minds=many minds see the same Dream, at the same time.