IB Philosophy 5.1.2 Arguments for the Existence of God Notes

Can Religious Claims Be Rationally Justified?

1. Topic 5.1.1 examined the nature of God, exploring what the word "God" means across different theistic traditions and analysing the divine attributes of classical theism: omnipotence, omniscience, timelessness, and omnibenevolence. This topic asks whether belief in the God described in 5.1.1 can be rationally justified through philosophical argument.
2. The IB syllabus poses two questions. First, can religious claims be rationally justified?
3. This is a question about whether reason alone, without appeal to faith, revelation, or scripture, can establish the existence of God.
4. Second, what role does religious tradition and practice play in shaping views about whether human reason can answer questions about God's existence?
5. The tradition of natural theology holds that the existence and attributes of God can be demonstrated through reason and observation of the natural world, without relying on divine revelation.
6. The arguments examined in this topic (ontological, cosmological, teleological) all belong to this tradition. They attempt to show that belief in God is not merely a matter of faith but can be supported by rational evidence.
7. However, some religious traditions are sceptical of natural theology. Karl Barth (1886-1968), the most influential Protestant theologian of the twentieth century, argued that human reason is too corrupted by sin to reach God independently.
8. Knowledge of God comes only through divine self-revelation, not through philosophical argument. This view suggests that the arguments examined here, even if logically valid, miss the point of how genuine religious knowledge is acquired.

Barth, Plantinga, and the Limits of Natural Theology

1. For Barth, a philosopher who constructs a logical proof of God's existence has not discovered God but constructed a human idea masquerading as the divine.
2. Genuine knowledge of God comes only when God chooses to reveal Himself, as in the Biblical encounter at the burning bush. For Barth, you cannot go hunting for God with logic; God has to show up first.
3. Reformed epistemology, developed by Alvin Plantinga, offers a middle position: belief in God can be properly basic, meaning it does not require argumentative support to be rational. Just as we accept the existence of the external world or other minds without proof, belief in God can be a foundational belief grounded in religious experience rather than philosophical demonstration.
4. The overarching Unit 5 question, "Can we prove the existence of a higher being through reasoning or experience?", frames the entire discussion. The arguments below attempt to do precisely this.
5. Whether they succeed depends on how we evaluate their premises, their logical structure, and the objections they face. Topic 5.1.3 will examine the counter-arguments.
6. The IB syllabus requires four specific arguments: the ontological argument, the cosmological argument (including the Kalam version), the teleological argument, and the argument from karma in Nyaya Hindu thought. Each takes a different approach to demonstrating God's existence, and each connects to the attributes of God discussed in 5.1.1.
7. Students should note that the arguments below target the God of classical theism (as defined in 5.1.1): an omnipotent, omniscient, omnibenevolent being. The arguments do not directly support polytheistic or pantheistic conceptions of the divine.
8. Descartes's versions of these arguments will be examined in the prescribed text (10.3.4), providing a further opportunity to analyse their strengths and weaknesses.

The Ontological, Cosmological, and Teleological Arguments

1. The ontological argument is unique among the proofs of God because it is entirely a priori (based on reason and logic alone, without looking at the world): it attempts to demonstrate God's existence from the concept of God alone, without appealing to any evidence or observation.
2. Anselm (discussed in 5.1.1) argued that God is "that than which nothing greater can be conceived": if God existed only in the mind but not in reality, then a greater being could be conceived, contradicting the definition.
3. Therefore God must exist both in the mind and in reality: this is the logical move at the heart of the ontological argument, and it is this step that most objectors challenge.
4. The monk Gaunilo of Marmoutiers objected in his 'On Behalf of the Fool': if Anselm's reasoning is valid, we could prove the existence of a perfect island by the same logic, since a conceivable perfect island that also exists in reality is greater than one that exists only in the mind.
5. Anselm replied that the argument applies only to 'that than which nothing greater can be conceived,' a unique case, and that islands (as finite objects) cannot be the subject of this definition, since we can always conceive of a greater island.