#how would you centralize this menu?

here's the CSS code:

<style type="text/css">

	ul.menu_horizontal {
	margin: 0 auto;
	padding: 0;
	list-style: none;
}
ul.menu_horizontal li {display: inline;}
ul.menu_horizontal li a{ 
	float: left;
	display: block;
	padding: 10px;
	color: #333;
	background: #eee;
	text-decoration: none;
}
ul.menu_horizontal li a:hover {
	background: #ccc;
}
</style>

# HERE IS THE LIST MENU:

<ul class="menu_horizontal">

	<li><a href="#">Home</a></li>
	<li><a href="#">História</a></li>
	<li><a href="#">Filosofia</a></li>
	<li><a href="#">Produtos</a></li>
	<li><a href="#">Contato</a></li>
	<br><br>
</ul>

# It's a horizontal menu, but it starts from left and not from center, i tried <center> inside the CSS and inside the class, the <li> but nothing