By the 1670s, Spinoza was advocating the following:
Spinoza, like most modern theorists, grounds the legitimacy of political authority in the self-interest of individuals. He argues not only that everyone, and every thing, for that matter, is driven by self-interest but that they ought to be as well. "The more every man endeavours and is able to seek his own advantage, the more he is endowed with virtue," he says in the Ethics. "To act in absolute conformity with virtue is nothing else in us but to act, to live, to preserve one's own being (these three mean the same) under the guidance of reason on the basis of seeking one's advantage." (pp.101-102)
So I am to be self-interested and to seek my own advantage, and to set my sights at the level of self-preservation. These ideas, so familiar within classical liberalism, are already present in the world view of Spinoza.
Stewart goes on to tell us that:
Spinoza did not invent the idea of a secular state founded on self-interest; rather, he observed it clearly for the first time ... The very features of modernity that were then and are still regarded by many as its signature evils - the social fragmentation, the secularity, and the triumph of self-interest - he enshrined as the founding virtues of the new world order. His political philosophy was, in essence, an active response to the challenges of modernity. (pp.102-103)
Here's some more:
According to the author of the Ethics, self-interest is a virtue itself. The political order he intended to establish is one in which all social goals are secular, and so none may transcend the self-realization of the individual. In his magnum opus he baldly avowed that "no virtue can be conceived prior to this one, namely, the drive to preserve oneself." (p.107)
From wikipedia we learn that Spinoza was a naturalist in his philosophy:
Spinoza rejects the dualistic assumption that mind, intentionality, ethics, and freedom are to be treated as things separate from the natural world of physical objects and events.
So Spinoza's challenge was to explain such things as intentionality, ethics and freedom naturalistically.
He could no longer assert the existence of an inherently existing good or evil:
Spinoza held a relativist's position, that nothing is intrinsically good or bad ...
Because Spinoza believed that nothing exists outside natural causes, he was a determinist who believed that all things were determined by natural laws:
... Spinoza believes in his deterministic universe that, "All things in nature proceed from certain necessity and with the utmost perfection." Therefore, nothing happens by chance in Spinoza's world ...
So how then did he ground his concepts of ethics and freedom? He took the philosophical idea of a "conatus" - a striving to continue to exist and thereby to preserve one's essence - as his general principle.
In Spinoza's view, we act virtuously if we act rationally to strive to exist, in accordance with this idea of a "conatus". Similarly, we are free inasmuch as we are not constrained from acting to preserve our essential being:
His concept of "conatus" states that human beings' natural inclination is to strive toward preserving an essential being and an assertion that virtue/human power is defined by success in this preservation of being by the guidance of reason as one's central ethical doctrine.
His goal is to provide a unified explanation of all these things [intentionality, ethics, freedom] within a naturalistic framework, and his notion of conatus is central to this project.
For example, an action is "free", for Spinoza, only if it arises from the essence and conatus of an entity. There can be no absolute, unconditioned freedom of the will, since all events in the natural world, including human actions and choices, are determined in accord with the natural laws of the universe, which are inescapable.
However, an action can still be free in the sense that it is not constrained or otherwise subject to external forces.
A couple of observations. First, it's not easy to integrate the different claims made by Spinoza. If everything that happens is both perfect and necessary, then how can you have different degrees of freedom and constraint?
Second, Spinoza identified a naturalistic aim of preserving one's own being and he grounded both virtue and freedom on an absence of external constraints in pursuing this aim.
This aim, though real and important, is nonetheless a narrow one to occupy an individual life and a human culture and civilisation. It was chosen because it helped to resolve certain difficulties within Spinoza's naturalistic philosophy.
The intellectual foundations of classical liberalism are neither persuasive nor appealing. Do we really wish to understand virtue in terms of rational self-interest? Is freedom really to be understood merely as an absence of external constraints in the pursuit of individual self-preservation?
As for the other plank of classical liberalism - a belief in the pursuit of material prosperity - Spinoza advocated this as a means of occupying the energies of the common man. It was his version of the "bread and circuses" which was supposed to keep the common man at a safe distance from the more substantial issues of life (Stewart, p.103).
There seems to be little to gain in rejecting modern liberalism in favour of more classical forms. We need to think independently of both of these political philosophies and assert a worthier and more fitting politics of our own.