Reddit mentions of I And Thou

Much like you, I've also recently developed a strong interest in Levinas. I've yet to read him, though, so please take that into account when considering my recommendations.

I recently asked some of my professors and a friend of mine who wrote his master's thesis on Levinas to help me out with getting started. This is what they recommended:

• This introductory book by Colin Davis has been the most recommended to me. Davis succeeds in the difficult task of executing a clear exposition of Levinas' difficult prose without sacrificing too much of its nuance.
  
• Regarding Levinas' own writing, begin with On Escape. This work develops Levinas' fundamental ideas on Being and alterity, demonstrates how he does phenomenology, and reveals his engagement with Heidegger and Husserl
  
• The two next best works to read are Existence and Existents and Time and the Other.
  
  I'm not too knowledgeable of Husserl, so all I can really recommend from him is the Cartesian Meditations, which sort of serves as an introduction to Husserl's own method of phenomenology.
  
  For Heidegger, the most important work in this regard is certainly Being and Time. If you have the time, I recommend picking up the Basic Writings and reading through most of it.
  
  On a final note, Levinas was steeped within the Jewish intellectual tradition. Jewish philosophers often emphasize the role of community and social contextuality in general. It might serve you well to read works such as Martin Buber's I and Thou and Gabriel Marcel's Being and Having.
  
  EDIT: Another good compliment to Levinas is Maurice Merleau-Ponty's Phenomenology of Perception.

I don't know if they're the strongest arguments, but I'll point you to some of the most interest ones.

First, a rather straightforward one, Paul Tillich's Dynamics of Faith. Tillich starts off talking about faith as a human phenomenon, but the latter half of the book veers off into Tillich's own brand of theism.

Secondly, Rudolf Otto's The Idea of the Holy, which analyzes the notion of holiness in much the same way that Tillich's book analyzes the notion of faith. This one is more structurally complex than the first, but like the first it's endgame is concerned with Otto's own existential protestantism.

Thirdly, Martin Buber's I and Thou takes a much less analytical approach. Buber's focus is on the nature of relation, and could be contrasted to both Otto's focus on the holy as a kind of experience.

Incidentally, all three of those are in the 150-200 page range, so apart from their increasing density of ideas, they ought to make for fairly short reads.

While you're at it, you might want to take a stab at Leo Tolstoy's The Kingdom of God is Within You. Yes, that Tolstoy. He was a Christian Anarchist. I haven't read it, so I can't promise you that it presents an argument for theism, but it should, if nothing else, present a novel view of Christian theism.

And lastly, the most recent heavyweight (in more sense than one) tome on the value of theism, which I'm gearing up to read myself, is Charles Taylor's A Secular Age. The general theme appears to be about the persistent vitality of religion amid the 18th-20th century growth of unbelief.

Beyond the obvious choices, Watts' The Book, Ram Dass' Be Here Now, Huxley's Doors of Perception, Leary’s The Psychedelic Experience, and of course Fear and Loathing (all of these should be on the list without question; they’re classics), here are a some others from a few different perspectives:

From a Secular Contemporary Perspective

Godel Escher Bach by Douglass Hofstadter -- This is a classic for anyone, but man is it food for psychedelic thought. It's a giant book, but even just reading the dialogues in between chapters is worth it.

The Mind’s Eye edited by Douglass Hofstadter and Daniel Dennett – This is an anthology with a bunch of great essays and short fictional works on the self.

From an Eastern Religious Perspective

The Tao is Silent by Raymond Smullyan -- This is a very fun and amusing exploration of Taoist thought from one of the best living logicians (he's 94 and still writing logic books!).

Religion and Nothingness by Keiji Nishitani – This one is a bit dense, but it is full of some of the most exciting philosophical and theological thought I’ve ever come across. Nishitani, an Eastern Buddhist brings together thought from Buddhist thinkers, Christian mystics, and the existentialists like Neitzsche and Heidegger to try to bridge some of the philosophical gaps between the east and the west.

The Fundamental Wisdom of the Middle Way by Nagarjuna (and Garfield's translation/commentary is very good as well) -- This is the classic work from Nagarjuna, who lived around the turn of the millennium and is arguably the most important Buddhist thinker after the Buddha himself.

From a Western Religious Perspective

I and Thou by Martin Buber – Buber wouldn’t approve of this book being on this list, but it’s a profound book, and there’s not much quite like it. Buber is a mystical Jewish Philosopher who argues, in beautiful and poetic prose, that we get glimpses of the Divine from interpersonal moments with others which transcend what he calls “I-it” experience.

The Interior Castle by St. Teresa of Avila – this is an old book (from the 1500s) and it is very steeped in Christian language, so it might not be everyone’s favorite, but it is perhaps the seminal work of medieval Christian mysticism.

From an Existentialist Perspective

Nausea by Jean Paul Sartre – Not for the light of heart, this existential novel talks about existential nausea a strange perception of the absurdity of existence.

The Myth of Sisyphus by Albert Camus – a classic essay that discusses the struggle one faces in a world inherently devoid of meaning.

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I’ll add more if I think of anything else that needs to be thrown in there!