Causation: An Early Modern Philosophical Dialogue

Foreword

This was our final for History of Modern Philosophy. It is a discourse between Spinoza, Hume, and Leibniz on the nature of causality. Just a fun little discourse, with maybe one original idea.

Body

Spinoza, Hume, and Leibniz walk into a tavern, in which they are regulars, engaged in a heated philosophical debate. Mark Stanley is bartending.

Leibniz: “Three beers, please.”

Mark: “Right away.”

The three go on murmuring about their debate.

Mark hands everyone their beer. The topic piques his interest, so he decides to lean in to eavesdrop on the discussion. Unfortunately, he slips and knocks Spinoza’s beer across the table.

M: “My goodness, apologies, Benedict. I was trying to listen to your enlightening discussion, but I should not have been lurking. I don’t know what I was thinking. Sorry for causing that.”

Spinoza: “Well, it wasn’t anything in your thoughts that caused it.”

M: “How do you mean?”

S: “It’s better not to get into it.”

M: “If this is one of your philosophical discourses, please, speak away.”

S: “Very well, sir. Nothing in your mind could have caused any effect in extension. Rather, there exists an infinite causal chain in each of God’s attributes. The ones we can name are mind and extension. They exist in parallel; each object’s attribute has a correlate in every other attribute. However, there is no causal interaction across attributes. For example, it was an infinite causal chain of extension that caused Mark’s extended body to knock over the beer; your mental state was simply parallel to it.”

M: “Intriguing. This makes a great deal of sense. However, Spinoza, I must ask, why are the mind and body separate? Though your narrative is coherent, this parallelism between extension, the mind, and all other attributes seems confusing. I intuitively think my intrigue caused me to lean on the table. Furthermore, only knowing two of the infinite attributes is worrisome. To me, it seems that our mental states are purely a consequence of our extended body.”

S: “Ah, but you are just misguided. Extension is nothing but what takes up space. It is conversely obvious that the mind, our thoughts, takes up no space in the world, correct?”

M: “Yes”

S: “Ergo, each individuated thought cannot be under extension. Furthermore, I have already clearly demonstrated that an infinite substance with infinite attributes must exist, namely God. All other conclusions simply follow a priori. Refer to 1P5, 1P7, 1P9, and 1P10 for more.”

Hume: “But Spinoza, how do you know about causality at all?”

S: “In my ethics, I show that God is the cause of all.” (1P15)

H: “Not your justification. Where do you show that things must have a cause?”

S: “I take it as an axiom, David” (1A3)

H: “This is exactly my project. We have seemingly granted causality prima facie acceptance. How can we claim to have causal knowledge?”

M: “How do you mean, Hume? Causality clearly exists. If I drop this glass of beer, surely it will shatter on the floor.”

H: “Understandable assertion. We first note the difference between matters of fact and relations of ideas. The latter speaks of the reasoning of the sciences, like math. The former speaks of everything else that we gain through experience, and can be logically contradicted. We learn about matters of fact through the experience of cause and effect. However, for any matters of fact to be logically sound, causality must be true a priori. Do we follow?” (E4)

M: “Yes.”

H: “Here lies the issue: one can only justify causality a posteriori. Sit and ponder, were you to be given two objects at random that you had not experienced, could you accurately predict the effect that could come from the cause?”

M: “No, Hume.”

H: “It is clear that all reason from causality is simply gained from experience. However, the problem runs deeper. Suppose you do drop that glass onto the floor. What will happen?”

M: “It will shatter!”

H: “Why?”

M: “Because I have dropped many glass objects and each time they have shattered.”

H: “Precisely the issue. The claim that previously similar objects have preceded certain effects and the claim that similar objects will in the future act similarly are distinct! Why would the former imply the latter?”

M: “Because historically, when I have noticed a pattern between things of similar appearance, they have in the future acted similarly.”

H: “Ah, but don’t you see the faulty logic? You are justifying the idea that the first claim implies the second by appealing to the first claim. This logic is circular. This is the problem with inductive reasoning. There is no non-circular logical justification. Thus, even though it may seem like you caused the beer to spill, we had no logical reason to believe that you slipping and colliding with the cup would cause the beer to spill.”

L: “This is quite intriguing, Hume. I have read your work and have a few questions. You claim that the claim that the sun will not rise tomorrow is no less intelligible than the claim that it will (E4). Yet, you also claim that all knowledge reduces to probability (A Treatise of Human Nature), yet also contradictorily assert that ‘there [can] be no such thing as chance in the world’ (E6). These claims seem contradictory!”

H: “Excellent inquiry, Leibniz. Let me first clarify that, like the Cartesian skeptic, just because we cannot prove causality exists, it doesn’t mean that I don’t believe it does. Now, I shall make clear the last two claims. The difference lies in the metaphysical and epistemological viewpoints of the world. Chance does not exist in the world, as it is determined; however, because we cannot reasonably know about the necessity of the building blocks of our world, the best we can do is simulate such necessary knowledge with probabilistic inference. To reconcile the first claim, probability does not remove us from the problem of induction. Suppose we make a similar observation that ‘With a certain probability, previous events preceded certain effects’ cannot justify ‘With a certain probability, future similar events will cause certain effects.’ without running into the same problem we have before!” (E6)

L: “Interesting ideas, Hume. However, I wish to put forward my own ideas, so long as everyone is interested.”

M: “Go ahead, Gottfried.”

L: “God clearly exists. Nothing between two substances is causal. Each substance has its own essence, which is all of its predicates through all time (D §8). Furthermore, within that essence is all of its interactions with everything else in the universe for all time (D §9). Furthermore, all substances are independent of one another and only depend on God. Thus, when something happens to a substance, it is because of the substance’s essence, not anything causal from the other objects; those are simply correspondences (D §14). Consider our example of the spilling of beer. It is not because you did anything to cause that beer to spill; rather, it was in that beer’s essence to be spilled by you at that very instant, the same instant in which it was a part of your essence to make contact with the beer.”

A clock strikes twelve.

M: “I wish I could spend more time interrogating your viewpoints, Leibniz. However, it is about closing time. I have much to think about for causal interaction, and many viewpoints to assess. Thank you.”