'if' not followed by conditional statement

I'm going through Zed's "Learn Python The Hard Way" and I'm on ex49. I'm quite confused by the following code he gives:

def peek(word_list):
    if word_list: # this gives me trouble
        word = word_list[0]
        return word[0]
    else:
        return None

The condition of the if statement is giving me trouble, as commented. I'm not sure what this means as word_list is an object, not a conditional statement. How can word_list, just by itself, follow if?