diff --git a/actor.ts b/actor.ts
index 8b5f0d2..8f055b6 100644
--- a/actor.ts
+++ b/actor.ts
@@ -11,9 +11,9 @@ export const retract = Symbol('retract');
 export const message = Symbol('message');
 
 export interface Entity {
-    [assert](turn: Turn, assertion: Assertion, handle: Handle): void;
-    [retract](turn: Turn, handle: Handle): void;
-    [message](turn: Turn, message: Assertion): void;
+    [assert]?(turn: Turn, assertion: Assertion, handle: Handle): void;
+    [retract]?(turn: Turn, handle: Handle): void;
+    [message]?(turn: Turn, message: Assertion): void;
 }
 
 export class Ref<T> {
@@ -104,10 +104,6 @@ export class Turn {
         return this._ensureActor(what).ref(t);
     }
 
-    entity(t: Partial<Entity>): Ref<Entity> {
-        return this.ref({ ... NULL_ENTITY, ... t }, "entity");
-    }
-
     spawn(bootProc: (t: Turn) => void, initialAssertions?: IdentitySet<Handle>): void {
         if ((initialAssertions !== void 0) && (initialAssertions.size > 0)) {
             this._ensureActor("spawn with initialAssertions");
@@ -131,7 +127,7 @@ export class Turn {
         const h = nextHandle++;
         this.enqueue(location.actor, t => {
             this.actor!.outbound.set(h, [location, assertion]);
-            location.target[assert](t, assertion, h);
+            location.target[assert]?.(t, assertion, h);
         });
         return h;
     }
@@ -149,7 +145,7 @@ export class Turn {
     _retract(location: Ref<Entity>, handle: Handle): void {
         this.enqueue(location.actor, t => {
             this.actor!.outbound.delete(handle);
-            location.target[retract](t, handle);
+            location.target[retract]?.(t, handle);
         });
     }
 
@@ -160,7 +156,7 @@ export class Turn {
     }
 
     message(location: Ref<Entity>, assertion: Assertion): void {
-        this.enqueue(location.actor, t => location.target[message](t, assertion));
+        this.enqueue(location.actor, t => location.target[message]?.(t, assertion));
     }
 
     enqueue(actor: Actor, a: LocalAction): void {
@@ -185,12 +181,6 @@ export class Turn {
     }
 }
 
-export const NULL_ENTITY: Entity = {
-    [assert](_t: Turn, _assertion: Assertion, _handle: Handle): void {},
-    [retract](_t: Turn, _handle: Handle): void {},
-    [message](_t: Turn, _assertion: Assertion): void {},
-};
-
 function extractFromMap<K, V>(map: Map<K, V>, keys?: IdentitySet<K>): Map<K, V> {
     const result: Map<K, V> = new Map();
     if (keys !== void 0) {
diff --git a/main.ts b/main.ts
index 0187821..0ef0399 100644
--- a/main.ts
+++ b/main.ts
@@ -111,7 +111,7 @@ Turn.for(null, async (t: Turn) => {
             valueHandle = t.replace(ds, valueHandle, BoxState(value));
         }
         setValue(t, 0);
-        t.assert(ds, Observe(SetBox.constructorInfo.label, t.entity({
+        t.assert(ds, Observe(SetBox.constructorInfo.label, t.ref({
             [message](t: Turn, [newValue]: [number]): void {
                 if (newValue % 25000 === 0) {
                     const endTime = Date.now();
@@ -131,7 +131,7 @@ Turn.for(null, async (t: Turn) => {
     t.spawn(t => {
         console.log('Spawning Client');
         let count = 0;
-        t.assert(ds, Observe(BoxState.constructorInfo.label, t.entity({
+        t.assert(ds, Observe(BoxState.constructorInfo.label, t.ref({
             [assert](t: Turn, [currentValue]: [number]): void {
                 // console.log(`Client: got ${currentValue}`);
                 if (currentValue === 300000) {
@@ -142,7 +142,7 @@ Turn.for(null, async (t: Turn) => {
                 }
             }
         })));
-        t.assert(ds, Observe(BoxState.constructorInfo.label, t.entity({
+        t.assert(ds, Observe(BoxState.constructorInfo.label, t.ref({
             [assert](_t: Turn, _assertion: Assertion): void { count++; },
             [retract](t: Turn, _handle: Handle) {
                 if (--count === 0) {