Wrong number of arguments error???

class Address
  attr_accessor :kind, :street_1, :street_2, :city, :state, :postal_code

  def initialize(kind, street_1, street_2, city, state, postal_code)
    @kind = kind or ''
    @street_1 = street_1 or ''
    @street_2 = street_2 or ''
    @city = city or ''
    @state = state  or ''
    @postal_code = postal_code or ''
  end

  def to_s(format = 'short')
    address = ''
    case format
    when 'long'
      address += street_1 + "\n"
      address += street_2 + "\n" if !street_2.nil?
      address += "#{city}, #{state} #{postal_code}"
    when 'short'
      address += "#{kind}: "
      address += street_1
      if street_2
        address += " " + street_2
      end
      address += ", #{city}, #{state}, #{postal_code}"
    end
    address
  end
end

address = Address.new
address.initialize('Home', '123 Main St.', '', 'Portland', 'OR', '97213')