When one says "G-d", what do you picture? An old man? Long white beard? Flowing white robes? Furrowing his eyebrows as he looks down on mankind?
What if you just pictured...
No, no, no, you will tell us. G-d can't be nothing! G-d made man in his own image, Genesis something or other! It's right there in the Torah!
Yeah, that doesn't exactly sit well with your religious upbringing, does it? So you can imagine the resistance that Philo of Alexandria felt when he proposed that very thing.
Philo tried to match Greek and Judaic philosophy, which really didn't get him off the right foot with contemporaries. One of the points he derived was that G-d existed outside of time and space, that he had no form, that he couldn't be perceived...
Makes a little more sense than an old man, no?